Method and apparatus for specimen fabrication

ABSTRACT

A specimen fabrication apparatus including: an ion source, an optical system for irradiating a projection ion beam to a sample, wherein the optical system includes a patterning mask to form a ion beam emitted from the ion source into the projection ion beam, a sample stage to mount the sample, a vacuum specimen chamber to contain the sample stage, a probe for separating a micro-specimen from the sample by irradiation of the projection ion beam, a specimen holder to fix the micro-specimen, wherein the projection ion beam is irradiated to the micro-specimen fixed to the specimen holder and extracted by the probe in the specimen chamber, so that a finish fabrication to the micro-specimen is enabled.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 11/390,201, filed Mar.28, 2006, which is a continuation of application Ser. No. 10/941,913,filed Sep. 16, 2004, which is a continuation of application Ser. No.10/395,237, filed Mar. 25, 2003 (now U.S. Pat. No. 6,828,566), which isa divisional of application Ser. No. 09/202,540, filed Dec. 16, 1998(now U.S. Pat. No. 6,538,254). This application relates to and claimspriority from Japanese Patent Application Nos. 9-196213, filed on Jul.22, 1997; 9-263185 and 9-262184, both filed on Sep. 29, 1997. Theentirety of the contents and subject matter of all of the above isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus forfabrication of a specimen. More particularly, the present inventionrelates to a method and an apparatus for extracting a micro-specimenincluding a specific small area of a semiconductor material such as asemiconductor wafer or a semiconductor device chip from thesemiconductor material by separation using an ion beam and forfabricating a specimen used for carrying out an observation, an analysisand/or a measurement of the specific small area.

2. Description of the Prior Art

In recent years, efforts made to shrink geometries of semiconductordevices make progress at a very great pace. In a structure analysis ofthese semiconductor devices, there has been demanded an observation of ananoscopic structure which is so small that, at a resolution of anordinary scanning electron microscope referred to hereafter simply as anSEM, the structure can not be observed any longer. As a result,observation by means of a transmission electron microscope which isabbreviated hereafter to a TEM is indispensable in place of an SEM.Traditionally, however, fabrication of a specimen for an observationusing a TEM can not help resorting to manual work which must be done bya well trained person and takes a long time. For this reason, inreality, the method for observation of a specimen using a TEM does notcome into wide use as the method for observation by means of an SEM,whereby a specimen can be fabricated with ease and results ofobservations can be thus be obtained immediately, did.

The conventional method for fabrication of a specimen for an observationby using a TEM is explained as follows. FIG. 2 is diagrams showing thefirst conventional method for fabrication of a specimen for observationusing a TEM. A specimen for observation using a TEM is also referred tohereafter simply as a TEM specimen. To be more specific, FIG. 2/(a) is adiagram showing a semiconductor wafer 2 on which LSIs were fabricated.The semiconductor wafer 2 is referred to hereafter simply as a wafer ora substrate. As shown in FIG. 2/(b), the wafer 2 comprises anupper-layer portion 2A and a lower-portion 2B or a substrate. Assumethat a specimen for TEM observation of a specific area on the wafer 2 isfabricated. First of all, a mark not shown in the figure is put on anarea 22 subjected to the observation using a TEM. By exercising care soas not to damage the area 22 to be observed, an injury is deliberatelyinflicted on the wafer 2 by using a tool such as a diamond pen in orderto cleave the wafer 2 or the wafer 2 is cut by means of a dicing saw inorder to take out a sliber chip 21 shown in FIG. 2/(b). In order to makethe center of a TEM specimen being created the area 22 to be observed,the areas 22 of two chips are stuck to each other by using adhesive 23to produce 2 specimens 24 stuck together as shown in FIG. 2/(c). Then,the two stuck specimens 24 are sliced by means of a diamond cutter toproduce slice specimens 25 shown in FIG. 2/(d). The dimensions of eachof the slice specimens 25 are about 3 mm×3 mm×0.5 mm. Then, the slicespecimen 25 is put on a grinding plate to be ground by using abrasivesinto a thin specimen, namely, a ground specimen 25′ with a thickness ofabout 20 microns. Subsequently, the ground specimen 25′ is attached to asingle-hole holder 28 mounted on-a TEM stage, that is, a stage forholding a TEM specimen as shown in FIG. 2/(e). Then, ion beams 27 areirradiated to the surfaces of the ground specimen 25′ as shown in FIG.2/(f). Sputtering fabrication (or ion-milling fabrication) is thencarried out on the center of the specimen 25′ as shown in FIG. 2/(g).Finally, when a hole has been bored through the center of the specimen25′, the irradiation of the ion beams 27 is halted as shown in FIG.2/(h). A thinned area 26 with a thickness not exceeding a value of about100 nm fabricated as described above has been observed by a TEM. Thismethod is described in references such as a book with a title of“High-Resolution Electron Microscope: Principle and Usage”, authored byHisao Horiuchi and published by Kyoritsu Syuppan, Page 182, and used asprior-art reference 1.

FIG. 3 is a diagram showing the second conventional method forfabrication of a TEM specimen. This method is a method for fabricationof a specimen using a focused ion beam which is abbreviated hereafter toan FIB. As shown in the figure, first of all, a mark not shown in thefigure is created by using a laser beam or an FIB in the vicinity of anarea 22 to be observed on the wafer 2 and then the wafer 2 is diced asshown in FIG. 3/(a). A sliver chip 21 shown in FIG. 3/(b) is then takenout from the wafer 2. The sliver chip 21 is further sliced to produceslice specimens 21′ shown in FIG. 3/(c). The dimensions of each of theslice specimens 21′ are about 3 mm×0.1 mm×0.5 mm which is the thicknessof the wafer 2. Then, the slice chip 21′ is ground into a thinnedspecimen 21″. The thinned specimen 21″ is then stuck to a TEM-specimenholder 31 which resembles a thin metallic disc plate and has a cutportion 31′ as shown in FIG. 3/(d). Subsequently, the area 22 to beobserved on the thinned specimen 21″ is further thinned by means of anFIB 32 so that only a slice 22′ having a thickness of about 100 nm isleft as shown in FIG. 3/(e), (f). The slice 22′ is used as a specimenfor an observation using a TEM. This method is described in documentssuch as a collection of theses with a title of “Microscopy ofSemiconducting Materials 1989”, Institute of Physics Series No. 100,Pages 501 to 506, which is used as prior-art reference 2.

FIG. 4 is a diagram showing the third conventional method forfabrication of a TEM specimen. The method is disclosed in JapanesePatent Laid-open No. Hei 5-52721 which is used as prior-art reference 3.As shown in the figure, first of all, a specimen substrate 2 is held insuch a posture that an FIB 32 is irradiated to the surface of thespecimen substrate 2 perpendicularly. The surface of the specimensubstrate 2 is then scanned by the FIB 32 along the circumference of arectangle to form a rectangular hole 33 with a sufficient thickness onthe surface as shown in FIG. 4/(a). Then, the specimen substrate 2 isinclined so that the surface thereof forms a gradient of about 70degrees with the axis of the FIB 32 and a bottom trench 34 forseparation is further created on a side wall of the rectangular hole 33as shown in FIG. 4/(b). The gradient angle of the specimen substrate 2is adjusted by using a sample stage which is not shown in the figure.Subsequently, the orientation of the specimen substrate 2 is restored toits original posture so that the FIB 32 is again irradiated to thesurface of the specimen substrate 2 perpendicularly and a trench 35 isfurther created as shown in FIG. 4/(c). Then, by driving a manipulatorfor holding a probe 36, the tip of the probe 36 is brought into contactwith the surface of a portion 40 of the specimen substrate 2 to beseparated as shown in FIG. 4/(d). It should be noted that themanipulator itself is not shown in the figure. In this state, the FIB 32is irradiated to a local area including the tip of the probe 36 whilegas 39 for deposition is being supplied from a gas nozzle 37 to createan ion-beam-assisted-deposition film 38 which is abbreviated hereafterto an IBAD film or a deposition film. In this way, the portion 40 of thespecimen substrate 2 to be separated and the tip of the probe 36 whichhave been brought into contact with each other are firmly joined to eachother by the deposition film 38 as shown in FIG. 4/(e). Finally,portions left around the portion 40 of the specimen substrate 2 to beseparated are separated by the FIB 32 to detach the portion 40 from thespecimen substrate 2 as shown in FIG. 4/(f). The detached portion 40separated from the specimen substrate 2 remains in a state of beingfirmly joined to the tip of the probe 36 as shown in FIG. 4/(g). An areaon the separated portion 40 to be observed is further thinned by usingan FIB to a thickness of about 100 nm to produce a specimen forobservation using a TEM.

The first and second conventional methods described above can not helpresorting to manual work requiring skills of a well trained personfabricating the specimen. The manual work includes grinding, mechanicalfabrication and sticking the specimen to the TEM-specimen holder. Inaddition, with these conventional methods, in order to fabricate adesired specimen, it is necessary to split the wafer or the substrate ofthe device chips into portions by cleaving or cutting the wafer or thesubstrate. In order to acquire a specimen of a desired area, portionsadjacent to the desired area are inevitably and/or inadvertently cleavedor cut. Assume that it is necessary to observe and/or analyze a portionother than an area which was subjected to an observation and/or ananalysis before. Since the substrate of the specimen was once cut inorder to fabricate specimens for the prior observation and/or analysis,an injury and/or a damage was inevitably and/or inadvertently inflictedupon the portion subjected to the next observation and/or analysis or apositional relation among portions to be observed and/or analyzed is nolonger known. As a result, there is raised a problem that accurateinformation on observations and/or analyses can not be obtainedcontinuously due to the inflicted injury and/or damage. In addition,while the ion milling and the process to thin a film by using an FIBdescribed above do not directly involve manual work, they have a problemof a long fabrication time which is difficult to solve.

Furthermore, in recent years, there is seen a trend of an increasingwafer diameter to 300 mm. The number of device chips that can befabricated from such a wafer also increase as well. In addition, thedevice itself has more added values. As a result, splitting a wafer intoportions by cleaving or cutting the wafer in order to observe and/oranalyze a particular area leads to a disposal to discard portions otherthe area to be observed and/or analyzed which is very uneconomical.Moreover, when a small particle or an abnormal shape is detected in acertain area during a scanning operation over the entire wafer bydriving a variety of microscopes, a cause of such a small particle orsuch an abnormal shape has to be clarified by conducting an observationand/or an analysis prior to the splitting a wafer into chips, inparticular, before the small particle disappears. Otherwise, a number ofdefective devices among final products will be resulted in, incurring aneven larger loss. If a plurality of specimens can be produced in a shortperiod of time without splitting the wafer into portions, observationsand/or analyses can be carried out very economically, giving rise to agreat contribution to improvements of a product manufacturing yield.

With the third conventional method, on the other hand, once a specimenis set on the sample stage, it is not necessary for the operator to domanual work directly till separation of micro-specimens and to cut thewafer carelessly. In this method, however, the separated specimenremains in a state of being attached to the tip of a probe so that, whenthe separated specimen is brought into an observation apparatus and/oran analyzer in such a state to be observed and/or analyzed, the specimenwill vibrate, raising a problem that it is impossible to obtain reliableresults of observation and/or analysis.

As the conventional TEM-specimen holder, a holder 78 with a single hole79 shown in FIG. 7/(a), a holder 80 with a notch 108 shown in FIG. 7/(b)and a holder 109 with a mesh shown in FIG. 7/(c) are known. Assume thatthe single-hole-type holder 78 or the notch-type holder 80 is used inthe third conventional method for specimen fabrication described aboveto hold a micro-specimen 40 with a small size in the range 20 to 30microns. In this case, it is necessary to adjust the position of themicro-specimen 40 on the inner wall of the notch 108 or the single hole79 with a high degree of accuracy, making the installation workdifficult to carry out. Such a problem is not encountered with themesh-type holder 109. This is because, by using a mesh-type holder 109with a gap between mesh nodes adjusted to the size of the micro-specimen40, the position at which the micro-specimen 40 is to be installed canbe selected arbitrarily to a certain degree. With the mesh-type holder109, however, an electron beam path 82 propagating toward an area 81 tobe observed is shielded by a mesh structure member 109′ as shown in FIG.7/(d), making an observation using a TEM impossible in some cases.

SUMMARY OF THE INVENTION

It is thus an object of the present invention to provide an improvedmethod for fabrication of a specimen capable of solving the problemsencountered in the conventional methods described above and to provide agood apparatus for fabrication of a specimen used for implementing theimproved specimen fabrication method.

To be more specific, it is a first object of the present invention toprovide a specimen fabrication method capable of fabricating a specimenof a small area to undergo an observation or a measurement/analysiscarried out by an observation apparatus such as a TEM or ameasurement/analysis apparatus to which the specimen is to betransferred without the need for a well trained person to do manual worksuch as grinding and dicing and the need to split a semiconductor waferor an LSI chip by cleaving or cutting.

It is a second object of the present invention to provide a goodspecimen fabrication apparatus used for implementing the specimenfabrication method provided as the first object of the invention.

It is a third object of the present invention to provide a TEM-specimenholder which is used in conjunction with a TEM and allows amicro-specimen extracted from a specimen substrate to be positioned withease.

In order to achieve the first object of the present invention describedabove, the present invention provides a specimen fabrication methodwhich comprises the steps of:

firmly joining the tip of a probe to the vicinity of an area on aspecimen substrate such as an LSI chip and a semiconductor wafer held ona sample stage to be subjected to a desired observation and/or ameasurement/analysis; (such an area is also referred to hereafter as anarea to be observed)

irradiating an ion beam to regions surrounding the vicinity of the areato be observed;

extracting and separating a micro-specimen including the area to beobserved from the specimen substrate by ion-beam sputtering fabrication;

conveying the extracted and separated micro-specimen with themicro-specimen firmly joined to the tip of the probe as it is to aTEM-specimen holder of an apparatus for conducting the desiredobservation and/or measurement/analysis by moving the probe or thesample stage;

firmly attaching the micro-specimen to the TEM-specimen holder;

separating the tip of the probe from the micro-specimen; and

carrying out the desired observation and/or measurement/analysis whichis also generically referred to hereafter simply as an observation.

In addition, in order to carry out the observation on a specific area tobe observed on the specimen substrate, before firmly joining the tip ofthe probe to the vicinity of the specific area to be observed, a markingprocess of putting a mark on the specific area is performed in order toclearly indicate the specific area. After the micro-specimen has beenseparated from the tip of the probe, an FIB is irradiated to thespecific area to be observed as indicated by the mark in order to carryout additional fabrication such as film thinning.

It should be noted that in the process of firmly joining the tip of theprobe to the vicinity of the specific area to be observed, the tip canbe joined to the vicinity through an ion-beam assist deposition film ora redeposition film created by ion-beam sputtering or joined by a fusionor metallic-junction technique.

In the process of separating the tip of the probe from themicro-specimen, on the other hand, an ion-beam sputtering fabricationmethod can be adopted. As an alternative, if a method of using adhesiveas a technique of firmly joining the tip of the probe to themicro-specimen, in the process of separating the tip of the probe fromthe micro-specimen, an UV-ray irradiation method or a heating method canbe adopted. As another alternative, a method of electrostatic absorptioncan be adopted as a technique of firmly joining the tip of the probe tothe micro-specimen.

In addition, in order to achieve the second object of the presentinvention described above, the present invention provides a specimenfabrication apparatus which comprises:

a movable sample stage on which a specimen substrate is mounted;

a probe connecting means for joining the tip of a probe to the vicinityof a desired area to be observed on the specimen substrate;

a micro-specimen separating means for separating a micro-specimenincluding the area to be observed from the specimen substrate with themicro-specimen joined to the tip of the probe as it is by irradiation ofan ion beam to regions surrounding the vicinity of the area to beobserved;

a micro-specimen fixing means for firmly fixing the. micro-specimenseparated from the specimen substrate to a TEM-specimen holder; and

a probe separating means for separating the tip of the probe from themicro-specimen firmly fixed to the TEM-specimen holder.

The sample stage comprises a sample cassette and a movable samplecassette holder for holding the sample cassette. The sample cassette isused for holding the TEM-specimen holder or a cartridge of theTEM-specimen holder which can be mounted and removed on and from thesample stage of the observation apparatus.

Typically, a probe exhibiting a spring effect can be used as theprobe-described above.

The probe connecting means typically comprises a probe contact means forbringing the tip of the probe into contact with the surface of thespecimen substrate, and a deposition-film forming means for forming anion-beam assist deposition film (an IBAD film) at the contact portionbetween the tip of the probe and the surface of the specimen substrate.Typically, the probe contact means has a manipulator mechanism forholding the probe and moving the probe relatively to the surface of thespecimen substrate. On the other hand, the deposition-film forming meanstypically comprises an ion-beam irradiating optical system forirradiating an ion beam to the contact portion between the tip of theprobe and the surface of the specimen substrate, and a gas supplyingmeans for supplying gas for assisted deposition to the contact portionto which the ion beam is irradiated. The tip of the probe is firmlyjoined to the surface of the specimen substrate through the IBAD filmformed by the deposition-film forming means.

The micro-specimen separating means has a configuration including anion-beam irradiating optical system for irradiating an ion beam to thespecimen substrate. The ion-beam irradiating optical system is typicallya PJIB (projection ion beam) irradiating optical system comprising anion source and a projection optical system for projecting ions emittedfrom the ion source on the specimen substrate as a PJIB. As analternative, the ion-beam irradiating optical system can be an FIB(focused ion beam) irradiating optical system comprising an ion sourceand a focusing optical system for irradiating ions emitted from the ionsource on the specimen substrate as an FIB. As another alternative, theion-beam irradiating optical system can be a combination of the PJIBirradiating optical system and the FIB irradiating optical system. Byirradiation of an ion beam which can be a PJIB or an FIB to the specimensubstrate by means of the ion-beam irradiating optical system, thespecimen substrate is subjected to sputter fabrication allowing themicro-specimen to be extracted and separated from the specimen surface.In addition, the micro-specimen separating means can also be configuredto include a first ion-beam irradiating optical system for irradiatingan ion beam to the specimen substrate from a first direction and asecond ion-beam irradiating optical system for irradiating an ion beamto the specimen substrate from a second direction different from thefirst direction. By providing the two ion-beam irradiating opticalsystems in this way, the process to extract a micro-specimen from thespecimen substrate can be carried out more easily. It should be notedthat, as the micro-specimen separating means, a laser-beam irradiatingoptical system or a combination of an ion-beam irradiating opticalsystem and a laser-beam irradiating optical system can also be used aswell.

Typically, the micro-specimen fixing means comprises a specimen contactmeans for bringing a micro-specimen into contact with an area on theTEM-specimen holder to fix the micro-specimen to the area and adeposition-film forming means for forming an ion-beam assist depositionfilm (an IBAD film) at the contact portion between the micro-specimenand the area on the TEM-specimen holder to fix the micro-specimen to thearea. The deposition-film forming means can have the same configurationas the deposition-film forming means employed in the probe contact meansdescribed earlier. The micro-specimen is firmly joined to the area onthe TEM-specimen holder to fix the micro-specimen to the area throughthe IBAD film formed by the deposition-film forming means.

The probe separating means is implemented typically by a means forirradiating an ion beam to the IBAD film through which themicro-specimen is firmly joined to the area on the TEM-specimen holder.By irradiation of an ion beam, the IBAD film fixing the tip of the probeto the micro-specimen is subjected to a sputtering process to remove theIBAD film, hence, allowing the tip of the probe to be pulled out fromthe micro-specimen.

It should be noted that the probe connecting means and themicro-specimen fixing means can also use a redeposition film formed byion-beam sputtering in place of an IBAD film or adopt a fusion ormetallic-junction method. In this case, the probe separating meansadopts the ion-beam sputtering fabrication. In addition, the probeconnecting means and the micro-specimen fixing means can also adopt anadhesion method or an electrostatic absorption method instead of themethods described above.

The specimen fabrication apparatus provided by the present invention mayinclude an observation unit for observing the surface of the specimensubstrate, the tip of the probe or the vicinity of the TEM-specimenholder. The observation unit typically comprises an electron-beamirradiating optical system for irradiating an electron beam to theaforementioned member to be observed, a secondary-electron detector fordetecting secondary electrons emitted by the observed member dueirradiation of the electron beam and a display sub-unit for displaying asecondary-electron image of the observed member by using a detectionsignal output by the secondary-electron detector. As an alternative, theobservation unit can also be implemented by an optical observationapparatus such as an optical microscope. By observing the member to beobserved using the observation unit, it is possible to obtaininformation on a contact/connection state between the tip of the probeand the surface of the specimen substrate, a separation state of themicro-specimen from the surface of the specimen substrate and acontact/connection state between the micro-specimen and the TEM-specimenholder.

In addition, the specimen fabrication apparatus provided by the presentinvention may also be provided with a detector for detecting acontact/connection state as well as a separation state between the tipof the probe and the surface of the specimen substrate, between themicro-specimen and the specimen substrate and between the micro-specimenand the TEM-specimen holder. The detector can make use of variations incontact resistance between the members brought into contact with eachother or variations in voltage contrast on the secondary-electron imagementioned above. By virtue of the detector, it is possible to obtaininformation on the contact/connection state and the separation statebetween the respective members with a high degree of accuracy.

The TEM-specimen holder typically comprises a metallic wire for holdingthe micro-specimen and a support unit for firmly supporting both theends of the metallic wire. In the configuration of the TEM-specimenholder, the micro-specimen is firmly held by the metallic wire, allowinga specimen holding system suitable for observation using a TEM to berealized.

Other objects of the present invention, its configurations and effectsprovided thereby will become apparent one after another from thefollowing detailed description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described by referring to thefollowing drawings wherein:

FIG. 1 is a diagram showing the basic configuration of a specimenfabrication apparatus as implemented by an embodiment of the presentinvention;

FIG. 2 is process explanatory diagrams showing an example of theconventional method for fabrication of a specimen to be observed byusing a TEM;

FIG. 3 is process explanatory diagrams showing another example of theconventional method for fabrication of a specimen to be observed byusing a TEM;

FIG. 4 is process explanatory diagrams showing a further other exampleof the conventional method for fabrication of a specimen to be observedby using a TEM;

FIGS. 5A, 5B and 5C are diagrams each showing a typical configuration ofmain elements composing an ion-beam irradiating optical system employedin a specimen fabrication apparatus provided by the present invention;

FIGS. 6A, 6B and 6C are diagrams each showing a typical configuration ofa probe driver employed in the specimen fabrication apparatus providedby the present invention;

FIG. 7 is diagrams each showing a typical configuration of theconventional TEM-specimen holder;

FIGS. 8A, 8B, 8C and 8D are diagrams each showing a typicalconfiguration of a TEM-specimen holder of a metallic-wire type employedin the specimen fabrication apparatus provided by the present invention;

FIGS. 9A and 9B are diagrams showing a typical method of mounting theTEM-specimen holder employed in the specimen fabrication apparatusprovided by the present invention on a sample cassette;

FIG. 10 is a diagram showing a typical method of mounting a TEM-specimenholder cartridge employed in the specimen fabrication apparatus providedby the present invention on a sample cassette;

FIG. 11 is explanatory diagrams used for describing a typicalconfiguration and the function of a probe with a spring effect employedin the specimen fabrication apparatus provided by the present invention;

FIG. 12 is a diagram showing an example of a method to heat a probe inthe specimen fabrication apparatus provided by the present invention;

FIG. 13 is diagrams showing an example of a method of junction based ona technique of electrostatic absorption between the probe and amicro-specimen in the specimen fabrication apparatus provided by thepresent invention;

FIG. 14 is a diagram showing an example of a method to heat aTEM-specimen holder in the specimen fabrication apparatus provided bythe present invention;

FIG. 15 is a diagram showing another example of the configuration of thespecimen fabrication apparatus provided by the present invention:

FIG. 16 is diagrams showing typical methods to separate a micro-specimenin another example of the configuration of the specimen fabricationapparatus provided by the present invention;

FIG. 17 is process explanatory diagrams showing another embodiment ofthe present invention for implementing a method for fabrication of a TEMspecimen;

FIG. 18 is process explanatory diagrams showing a further otherembodiment of the present invention for implementing a method forfabrication of a TEM specimen;

FIG. 19 is a diagram showing the basic configuration of a specimenfabrication apparatus as implemented by another embodiment of thepresent invention;

FIGS. 20A, 20B and 20C are diagrams each showing a typical configurationof a specimen transferring unit employed in the specimen fabricationapparatus provided by the present invention;

FIG. 21 is explanatory diagrams each showing a location at which thespecimen transferring unit employed in the specimen fabricationapparatus provided by the present invention is installed;

FIG. 22 is diagrams showing an example of a method to install aTEM-specimen holder in the specimen fabrication apparatus provided bythe present invention;

FIG. 23 is diagrams showing another example of a method to install theTEM-specimen holder in the specimen fabrication apparatus provided bythe present invention;

FIG. 24 is diagrams showing a further other example of a method toinstall the TEM-specimen holder in the specimen fabrication apparatusprovided by the present invention;

FIG. 25 is a diagram showing a still further other example of a methodto install the TEM-specimen holder in the specimen fabrication apparatusprovided by the present invention;

FIG. 26 is explanatory diagrams each showing an embodiment implementingthe TEM-specimen holder in the specimen fabrication apparatus providedby the present invention;

FIG. 27 is process explanatory diagrams showing a method for fabricationof a specimen as implemented by another embodiment of the presentinvention;

FIG. 28 is a diagram showing another typical configuration of a specimentransferring unit employed in the specimen fabrication apparatusprovided by the present invention;

FIG. 29 is diagrams showing a procedure for bringing the tip of a probeinto contact with the surface of a specimen substrate by using thespecimen transferring unit shown in FIG. 28; and

FIG. 30 is a flowchart used for explaining the procedure for bringingthe tip of a probe into contact with the surface of a specimen substrateshown in FIG. 29.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will become more apparent from a careful study ofthe following detailed description of some preferred embodiments withreference to the accompanying diagrams.

First Embodiment

FIG. 1 is a diagram showing the basic configuration of a specimenfabrication apparatus as implemented by an embodiment of the presentinvention.

As shown in the figure, the specimen fabrication apparatus implementedby the embodiment of the present invention comprises:

an ion-beam irradiating optical system 1 for irradiating an ion beam 13to a specimen substrate 2 of a specimen, that is, an object ofobservation, such as a semiconductor wafer or a semiconductor chip;

a sample stage 3 for moving the specimen substrate 2 mounted thereon;

a sample-stage position controller 3′ for controlling the position ofthe sample stage 3 in order to identify a portion of the specimensubstrate 2 to be observed or an area to be observed;

a probe driver 4 for holding and moving a probe 11;

a probe-driver controller 4′ for controlling the probe driver 4;

a deposition-gas supplying source 8 for supplying deposition gas, thatis, gas used for deposition, to the vicinity of the area on the specimensubstrate 2 to be observed;

a deposition-gas supplying source controller 8′ for controlling thedeposition-gas supplying source 8;

an electron-beam irradiating optical system 9 for irradiating anelectron beam 16 to the surface of the specimen substrate 2; and

a secondary-electron detector 12 for detecting secondary electronsemitted by the surface of the specimen substrate 2.

Note that it is needless to say that the ion-beam irradiating opticalsystem 1, the sample stage 3, the probe driver 4, the deposition-gassupplying source 8, the electron-beam irradiating optical system 9 andthe secondary-electron detector 12 are laid out in a vacuum chamber 77which is put in a state at a high degree of vacuum.

The sample stage 3 comprises a sample cassette 17 for mounting thespecimen substrate 2 and a cassette holder 18 for firmly holding thesample cassette 17. The sample stage 3 is also provided with aTEM-specimen holder clasp 20 for holding a TEM-micro-specimen holder 19which is also referred to hereafter as a TEM holder. The TEM-specimenholder 19 is used for holding a micro-specimen separated from thespecimen substrate 2 mounted on the sample stage 3 and introducing themicro-specimen into an observation/analysis apparatus such as a TEMwhich is not shown in the figure. The sample stage 3 is controlled anddriven by the sample-stage position controller 3′ in order toarbitrarily set the orientation of the specimen substrate 2 in the3-dimensional directions as well as a tilt angle and a rotation angle ofthe specimen substrate 2 with respect to the axis of the ion beam 13. Inthis way, an irradiation position (or a fabrication position) of the ionbeam on the surface of the specimen substrate 2 as well as a glancingangle and a rotation angle of the ion beam 13 with respect to thesurface of the specimen substrate 2 can be set arbitrarily.

The ion-beam irradiating optical system 1 irradiates an ion beam 13 toregions on the surface of the specimen substrate 2 surrounding the areato be observed in order to separate or to cut out a micro-specimenincluding the area to be observed from the specimen substrate 2 byadopting the ion-beam sputtering fabrication method. The ion beam 13 isused as an assist ion beam in a ion-beam assist deposition method(abbreviated to as an IBAD method) for firmly joining the tip of theprobe 11 to the surface of the specimen substrate 2 in the vicinity ofthe area to be observed. In addition, the ion beam 13 is also used as anassist ion beam in the IBAD method for firmly joining a micro-specimenseparated from the specimen substrate 2 to the TEM-specimen holder 19.Finally, the ion beam 13 is also used in an ion-beam sputteringfabrication for separating or detaching the tip of the probe 11 from themicro-specimen which was firmly joined to the TEM-specimen holder 19.The ion-beam irradiating optical system 1 is driven and controlled by anion-beam driver 7.

The probe driver 4 is a so-called manipulator used for bringing the tipof the probe 11 into contact with the vicinity of the area to beobserved on the surface of the specimen substrate 2 and for conveying amicro-specimen separated from the specimen substrate 2 to theTEM-specimen holder 19 with the micro-specimen firmly joined to the tipof the probe 11. The probe driver 4 is driven and controlled by theprobe-driver controller 4′.

The deposition-gas supplying source 8 supplies deposition gas to thevicinity of the area to be observed on the surface of the specimensubstrate 2 to form a deposition film by using the IBAD method. The tipof the probe 11 is firmly joined to the surface of the specimensubstrate 2 through the deposition film. The deposition gas is also usedfor firmly joining the micro-specimen separated from the specimensubstrate 2 to the TEM-specimen holder 19 by using the IBAD method. Asthe deposition gas, hexacarbonyl tungsten [W(CO)6] is typically used. Toput it in detail, while the gas is being supplied to a space betweenmembers to be firmly joined to each other, that is, between the tip ofthe probe 11 and the surface of the specimen substrate 2 or between themicro-specimen and the TEM-specimen holder 19, an ion beam 13 isirradiated to the space to form a tungsten film (W film) therein. It isthe W film that firmly joins the members to be connected to each other.In order to separate the tip of the probe 11 from the micro-specimenwhich have been firmly joined to each other by the W film, on the otherhand, an ion beam 13 is irradiated to the W film. In this way, the Wfilm for joining the tip of the probe 11 to the micro-specimen isremoved by an ion-beam sputtering method which is abbreviated to an IBSmethod to the tip of the probe 11 from the micro-specimen. Thedeposition-gas supplying source 8 is driven and controlled by thedeposition-gas supplying source controller 8′.

The electron-beam irradiating optical system 9 and thesecondary-electron detector 12 constitute an observation unit forobserving the surface of the specimen substrate 2 by using an SEM(scanning electron microscope) method. The observation unit irradiatesan electron beam 16 emitted from the electron-beam source 14 to thesurface of the specimen substrate 2 while sweeping the electron beam 16in a scanning operation over the surface of the specimen substrate 2 bymeans of a deflector lens 15. Secondary electrons emitted by the surfaceof the specimen substrate 2 are detected by the secondary-electrondetector 12 to be displayed as an SEM (scanning electron microscope)image of the surface of the specimen substrates on a display sub-unit(CRT) 5. It should be noted that this observation unit is also used forobserving the vicinity of the tip of the probe 11 and the vicinity ofthe TEM-specimen holder 19. By such observation, it is possible toverify conditions and states such as the condition of the surface of thearea to be observed, the state of separation of the micro-specimen fromthe specimen substrate 2, the state of joining of the tip of the probe11 to the surface of the specimen substrate 2, the state of joining ofthe micro-specimen to the TEM-specimen holder 19 and the state ofseparation of the TEM-specimen holder 19 from the micro-specimen. Itshould be noted that the state of separation of the micro-specimen fromthe specimen substrate 2 can also be verified by detecting changes involtage contrast of the SEM image. In addition, the state of joining andthe states of separation can also be verified by detecting changes inelectrical resistance (or contact resistance) between the probe 11 andthe sample stage 3. The electron-beam irradiating optical system 9 isdriven and controlled by an electron-beam driver 10.

It is worth noting that, since the size of the micro-specimen extractedfrom the specimen substrate 2 is in the range 10 to 100 microns square,an optical microscope can be used as a surface observing means.

It should be noted that the sample-stage position controller 3′, theprobe-driver controller 4′, the ion-beam driver 7, the deposition-gassupplying source controller 8′, the electron-beam driver 10 and thedisplay sub-unit 5 are controlled by a central processing unit (CPU) 6which serves as a central controller.

The following is a description of configurations of components composingthe specimen fabrication apparatus presented in concrete terms and adescription of processes implementing the method for fabrication of aspecimen using the apparatus.

1-1[Ion-Beam Irradiating Optical System]

FIG. 5A is a diagram showing a typical configuration of main elementscomposing an ion-beam irradiating optical system 1 for irradiating aprojection ion beam (PJIB). As shown in the figure, an ion beam emittedby an ion source 41 is irradiated to a stencil mask 44 by a beamlimiting aperture 42 and an illumination lens 43. The ion beam passingthrough an opening 45 of the stencil mask 44 is then irradiated to thesurface of the specimen substrate 2 mounted on the sample stage 3 by aprojection lens 46. A PJIB 13 formed in this way fabricates a figuresimilar to the opening 45 on the surface of the specimen substrate 2. Inthe case of a PJIB, the divergence of the ion beam right after leavingthe ion source 41 does not have a direct effect on aberration. Thus, theion-beam limiting angle provided by the beam limiting aperture 42 can beset at a large value. As a result, the magnitude of the ion-beam currentcan be increased, giving rise to a characteristic of a high fabricationspeed.

By designing the opening 45 provided on the stencil mask 44 into arectangular pattern with a side 48 thereof passed through by the opticalaxis 47 as shown in FIG. 5B, the amount of side blurring of the PJIB 13corresponding to the side 48 can be made extremely small so that theresolution of a corresponding dent formed on the specimen substrate 2 bycontinuous projection of the PJIB 13 can be increased. As a result, afabricated surface corresponding to the side 48 is a cross-sectionalsurface perpendicular to the surface of the specimen substrate 2. Byproviding a rectangular opening 45 with a side 48 thereof passingthrough the optical axis 47 as described above, it is possible to createa structure with its wall surface erectly cut in the perpendiculardirection. For more information on this, refer to Japanese PatentLaid-open No. Hei 9-162098 with a title of the invention “Method andApparatus for Ion-Beam Fabrication”.

On the other hand, FIG. 5C is a diagram showing a typical configurationof main elements composing an ion-beam irradiating optical system 1 forirradiating a focused ion beam (FIB). As shown in the figure, an ionbeam emitted by an ion source 41 is formed into a focused ion beam (FIB)52 after passing through a beam limiting aperture 42′, a condenser lens49 for suppressing divergence of the ion beam and focusing the ion beamand an objective lens 50 for focusing the ion beam on the surface of thespecimen substrate 2. By sweeping the focused ion beam 52 in a scanningoperation over the surface of the specimen substrate 2 using a deflector51, an area with the scanning shape on the specimen substrate 2 isfabricated. By using such a focused ion beam 52, fabrication can becarried out with a high degree of precision. In addition, the FIBirradiating optical system 1 can also be used as a means for observingthe surface of the specimen substrate 2. In order to maintain the highfocusing ability of the focused ion beam 52 which is used to implementfabrication with a high degree of precision, however, it is necessary tosuppress chromatic aberration and spherical aberration. In order tosuppress the chromatic aberration and the spherical aberration, it isnecessary to limit the aperture angle of the ion beam by means of thebeam limiting aperture 42′. In consequence, the magnitude of theion-beam current can not be increased to a large value. As a result, theFIB irradiating optical system 1 has a shortcoming that the fabricationspeed is not so high. It should be noted that there are some methods toincrease the fabrication speed such as an FIB (focused ion beam)assisted etching method whereby sputtering is carried out while reactivegas is being supplied to the surface of the specimen substrate 2. Inorder to use the focused ion beam 52 as an observation means, it isnecessary to execute the steps of scanning the surface of the specimensubstrate 2 by the focused ion beam 52, detecting secondary electrons 53emanating from the surface of the specimen substrate 2 by means of thesecondary-ion detector 12 and displaying an image representing thesecondary electrons 53.

As described above, if a PJIB is used as an ion beam for fabrication ofa specimen, there is offered a merit that high-speed fabrication can beimplemented. If an FIB is used as an ion beam for fabrication of aspecimen, on the other hand, gained merits are a capability ofimplementing high-precision fabrication and an ability of the FIBirradiating optical system to also serve as an observation means.

1-2 [Probe Driver]

FIGS. 6A, 6B and 6C are diagrams each showing a typical configuration ofthe probe driver 4. As shown in FIG. 6A, the probe driver 4 isintroduced into the inside of the vacuum chamber 77 from the outsidethereof through a window 62 on a side wall 54 of the vacuum chamber 77.In this structure, the probe 11 can be moved independently of the samplestage 3 and, in addition, the probe 11 can be moved to the specimensubstrate 2 and the TEM-specimen holder 19 with ease.

As shown in FIG. 6A, the probe driver 4 comprises 2 units, namely, acoarse-movement actuator 56 and a fine-movement actuator 55. A coarsemovement of the probe 11 driven by the coarse-movement actuator 56 inthe X-axial direction of a coarse-movement shaft 65 takes place due to aforce which is generated as a result of expanding and shrinking a spring60 by means of an adjustment screw 57 for sliding a shaft 59. A coarsemovement of the probe 11 in the Z-axial direction takes place due to aforce which is generated as a result of expanding and shrinking a spring61 by means of an adjustment screw 58 for swinging the shaft 59 around asupporting point 63. A coarse movement of the probe 11 in the Y-axialdirection takes place in accordance with the same principle as thecoarse movement in the Z-axial direction except that an adjustment screwfor a coarse movement in the Y-axial direction is not shown in thefigure. The adjustment screw for a coarse movement in the Y-axialdirection is provided at a location in front of this drawing paper. Thesprings 60 and 61 are used for pressing the shaft 59 against the ends ofthe adjustment screws 57 and 58 respectively. A spring for a coarsemovement in the Y-axial direction which is not shown in the figure isinstalled in the same way as the spring 61 for a coarse movement in theZ-axial direction. As will be described below, the positional precisionof the coarse-movement actuator 56 has a value smaller than the strokeof a fine-movement actuator 55. Required of as compact a design aspossible, the fine-movement actuator 55 employs a piezoelectric device.Particularly, in the case of this embodiment, a bimorph-typepiezoelectric device is selected. The bimorph-type piezoelectric deviceoffers a merit of a relatively large movement range of at least severalhundreds of microns in comparison with piezoelectric devices of othertypes. On the other hand, since the coarse-movement actuator 56 is notrequired of a high positional precision, the coarse-movement actuator 56can be manufactured with ease. In addition, it is sufficient to controlthe position of the tip of the probe 11 at a micron order. Thus, abimorph-type piezoelectric device which has a relatively poor resolutionin comparison with piezoelectric devices of other types is capable ofsatisfying this requirement.

FIG. 6B is a diagram showing a typical configuration of thefine-movement actuator 55 employing 3 bimorph-type piezoelectric devicesfor fine movements in the 3 axial directions respectively in concreteterms. To be more specific, the fine-movement actuator 56 employsbimorph-type piezoelectric devices 66, 67 and 68 for fine movements inthe X, Y and Z axial directions respectively as shown in the figure. Aprobe holder 70 fixes the probe 11 to a 3-axial-direction fine-movementunit, that is, the movement-side end of the bimorph-type piezoelectricdevice 68. The fixed-side end of the bimorph-type piezoelectric device67 is firmly joined to a coarse-movement shaft 65 through afine-movement-unit fixing fixture 69. The bimorph-type piezoelectricdevices 66, 67 and 68 can each be driven by applying a simple voltagewithout requiring a special circuit. By utilizing the bimorph-typepiezoelectric devices 66, 67 and 68 in this way, a compact fine-movementactuator 55 offering a large stroke can be realized more economically. Areason why it is necessary to build a compact fine-movement actuator 55is described as follows.

In the case of a specimen substrate 2 fabricated by using a focused ionbeam (FIB) 52 explained earlier by referring to FIG. 5C, the shorter thedistance from the objective lens 50 to the specimen substrate 2, thehigher the degree to which the fabrication precision can be improved. Inaddition, in the case of a specimen substrate 2 fabricated by using aprojected ion beam (PJIB) 13 explained earlier by referring to FIG. 5A,the shorter the distance from the projection lens 46 to the specimensubstrate 2, the greater the value to which the projection magnificationof the opening 45 can be increased. That is, in the case of either ionbeam in use, it is desirable to have a short distance between thespecimen substrate 2 and the lens at the last stage. In consequence, thevolumes of the space between the specimen substrate 2 and the lens atthe last stage and the surrounding space are limited. In the spacesurrounding the specimen substrate 2, among other components, theobservation means, the secondary-electron detector 12, a deposition-gassupplying nozzle 8 and, in some cases, a nozzle for supplying gas forassist etching are provided. In order to avoid interference with thesecomponents, the end of the probe driver 4, that is, the fine-movementactuator 55, has to be made as compact as possible.

In the conventional technology shown in FIG. 4, the manipulator forconveying a micro-specimen separated from a specimen substrate comprisesbimorph-type piezoelectric devices for movements in the 3 axialdirections. However, a location at which the manipulator is installed isnot clarified. However, the conventional method for fabrication of aspecimen of FIG. 3 described in an official report can be interpretedthat the manipulator is mounted on the sample stage. With themanipulator mounted on the sample stage, in the case of an area to beobserved existing at the center of the wafer, a distance from theinstallation position of the manipulator to the area to be observed ismuch longer than the movement stroke of the manipulator. As a result, inthe conventional technology whereby the manipulator is mounted on thesample stage, there is raised a fatal problem of an inability to reachsuch an area to be observed.

On the other hand, the probe driver 4 shown in FIG. 6A is separated awayfrom the sample stage 3 so that, even if an area to be observed existsat the center of a large sample (wafer), the area can be accessedwithout problems. In addition, when the probe 11 is not in use, thecoarse-movement actuator 56 is capable of moving the probe 11 and thefine-movement actuator 55 over a long distance to preserved locations togive no hindrance to other components.

Another typical configuration of the probe driver 4 is shown in FIG. 6C.In this embodiment, a first probe driving mechanism 76 provided withboth the coarse-movement and fine-movement functions is sufficientlyseparated from the sample stage 3. A second probe driving mechanism 72is attached to the movement-side end of the probe driving mechanism 76through an extension rod 71. Implemented by a bimorph-type piezoelectricdevice, the second probe driving mechanism 72 has only the fine-movementfunction in the Z-axial direction. The probe 11 is firmly fixed to themovement-side end of the second probe driving mechanism 72. Incomparison with the configuration shown in FIG. 6B, this configurationoffers the following merits. In the case of the configuration shown inFIG. 6B, the probe 11 is driven in the X, Y and Z axial directions bythe respective bimorph-type piezoelectric devices. Each of thebimorph-type piezoelectric devices has one end thereof serving as afixed supporting point and the other end swinging to bend the device.That is, the other end moves along an arc-shaped locus in accordancewith an applied voltage. Strictly speaking, in a movement on the XYplane, driven only by 1 bimorph-type piezoelectric device, for example,by the piezoelectric device 66 for movements in the X-axial direction,the tip of the probe 11 does not move in the X-axial direction along atruly straight line, that is, the tip of the probe 11 does not move inthe X-axial direction with a high degree of accuracy. Thus, with thefine-movement actuator 55 comprising the 3 bimorph-type piezoelectricdevices 66, 67 and 68, in order to move the tip of the probe 11 to adesired location with a high degree accuracy, it is necessary to moveeach of the 3 bimorph-type piezoelectric devices 66, 67 and 68 by takingthe movements of the others into consideration. As a result, there israised a problem of complex operations to drive the 3 bimorph-typepiezoelectric devices 66, 67 and 68 in such a manner that theirmovements are dependent on each other. In order to solve this problem,it is necessary to employ a probe driving mechanism that is capable ofmoving the probe 11 along a straight line with a high degree ofaccuracy. If the probe driving mechanism is also required to have acapability of moving the probe 11 by a long stroke in the range 100microns to several mm as well as a resolution better than the micronorder, the structure of the probe driving mechanism will becomecomplicated and will become big in size in comparison with abimorph-type piezoelectric device. As a result, a problem of positionalinterference with other components surrounding the sample stage 3 willremain to be solved.

In the case of the probe driver 4 shown in FIG. 6C, on the other hand,the first probe driving mechanism 76 comprises an X-axial-directionactuator 73, a Y-axial-direction actuator 74 and a Z-axial-directionactuator 75 each having a stroke of about 5 mm and a movement resolutionof 0.1 microns to form a structure equipped with both thecoarse-movement and fine-movement functions. As described above, avariety of other components coexist in a layout between the lens 46 or50 provided at the last stage as shown in FIG. 5A or 5C respectively andthe substrate. In the configuration of the probe driver 4 shown in FIG.6C, the probe driver 4 is relieved of contention for space with theother components, allowing a micro-specimen to be extracted and conveyedwith ease.

By employing the probe driver 4 described above, the tip of the probe 11can be positioned on the surface of the specimen substrate 2 at aresolution of the sub-micron order. In addition, since the probe 11 canbe moved independently of the sample stage 3 by not mounting the probedriver 4 on the sample stage 3, an access by the tip of the probe 11 tothe specimen substrate 2 and the TEM-specimen holder 19 can be made withease.

It is possible to verify the state of joining of the tip of the probe 11to the surface of the specimen substrate 2, the state of separation ofthe micro-specimen from the specimen substrate 2, the state of joiningof the micro-specimen to the TEM-specimen holder 19 and the state ofseparation of the TEM-specimen holder 19 from the micro-specimen bydetecting changes in voltage contrast of a secondary-electron imageobtained from a detection signal generated by the secondary-electrondetector 12. These states can also be verified by monitoring a contactresistance between the probe 11 and the sample stage 3 and detecting achange in detected contact resistance.

1-3 [TEM-Specimen Holder]

FIGS. 8A, 8B, 8C and 8D are diagrams each showing a typicalconfiguration of the TEM-specimen holder 19 in concrete terms. TheTEM-specimen holder 19 shown in FIG. 8A has a structure wherein ametallic wire 83 is firmly attached to a donut-like fixed unit having anotch 84′. The metallic wire 83 has a diameter in the range 10 to 500μmφ. The fixed unit 84 has dimensions that allow the fixed unit 84 to bemounted on a stage for introducing an ordinary TEM specimen. Such astage is referred to hereafter as a TEM stage. In this embodiment, thefixed unit 84 has an external diameter of 3 mmφ. Effectiveness of theTEM-specimen holder 19 of the metallic-wire type is explained asfollows.

In order to separate a micro-specimen 40 from the specimen substrate 2,it is necessary to separate the bottom surface of the micro-specimen 40from the specimen substrate 2. Such separation is referred to hereafteras bottom dividing. In the bottom dividing by means of an ion beam, itis necessary to carry out fabrication wherein the ion beam is radiatedto the surface of the specimen substrate 2 in slanting direction withrespect to the surface. Thus, the bottom surface of the micro-specimen40 has 2 inclinations, namely, an incident angle of the ion beamradiated during the bottom-dividing and an aspect ratio of fabrication.By using the TEM-specimen holder 19 of the metallic-wire type describedabove, however, a micro-specimen 40 can be brought into contact with themetallic wire 83 correctly with a cross-sectional surface of a desiredobservation area 86 oriented perpendicularly as it is even if themicro-specimen 40 has the bottom inclinations. Refer to FIG. 8D. Assumethat a micro-specimen 40 with an area of 10 microns×30 microns and adepth of 10 microns is cut out from a specimen substrate 2 byfabrication using an ion beam with the sample stage 3 inclined at anangle of 60 degrees. In this case, the diameter of the metallic wire 83that does not put a desired observation area 86 under a shadow has avalue in the range 40 to 50 μmφ. By mounting the micro-specimen 40 onthe TEM-specimen holder 19 of the metallic-wire type, a contact portionon the metallic wire 83 between the micro-specimen 40 and the metallicwire 83 can be selected with a high degree of freedom. In addition, anelectron beam 82 passing through the desired observation area 86 can beprevented from being shielded by the metallic wire 83 as shown in FIG.8B.

Also in a TEM-specimen holder 19 of the metallic wire type having ametallic-wire fixing unit 85 as shown in FIG. 8C, the same effects asthose described above can be obtained. In addition, by firmly attachinga plurality of micro-specimens 40-1, 40-2 and 40-3 to a metallic wire 83as shown in FIG. 8D, the same plurality of micro-specimens 40-1, 40-2and 40-3 can be brought into a TEM at one time to give a merit of anincreased efficiency of the observation using a TEM. By using aTEM-specimen holder 19 of the metallic wire type as described above, aninfinitesimal micro-specimen can be mounted with ease and the path of anelectron beam for observation using a TEM can be prevented from beingshielded by the metallic wire 83.

1-4 [Sample Cassette and TEM-Specimen Holder]

FIGS. 9A and 9B are diagrams each showing a typical configuration formounting a TEM-specimen holder 19 on a sample cassette 17. In theseconfigurations, the TEM-specimen holder 19 of the metallic-wire typeshown in FIG. 8A is used as a TEM-specimen holder 19. FIG. 9A isdiagrams showing the entire sample cassette 17 and an enlarged portionof it, that is, a portion enclosed in a dotted-line circle. As shown inthe figure, a trench for seating the TEM-specimen holder 19 is createdon the sample cassette 17. The TEM-specimen holder 19 is fixed, beingsandwiched by the end surface of the trench and the TEM-specimen holderclasp 20. At that time, the TEM-specimen holder 19 is set up so that theposition of the metallic wire 83 employed in the TEM-specimen holder 19in the perpendicular direction is made close to a position on thesurface of the specimen substrate 2 and a position holding amicro-specimen 40 to be extracted is placed at the same level as thesurface of the specimen substrate 2. In this posture of the TEM-specimenholder 19, it is not necessary to move the probe 11 much up and down inthe Z-axial direction, allowing a high-speed access to a desiredlocation by the probe 11 to be made with ease. In addition, thepossibility that an injury is inflicted on the sample can be reduced. Inthe configuration shown in FIG. 9B, a plurality of trenches 20-1, 20-2,20-3 and 20-4 for seating TEM-specimen holders 19 are provided on thesample cassette 17. In this configuration, since a plurality ofTEM-specimen holders 19-1, 19-2, 1903 and 19-4 can be mounted on thesample cassette 17 at the same time, a plurality of micro-specimens 40can be extracted from the same specimen substrate 2 in an operationcarried out only once to put the sample chamber 77 in a vacuum state,allowing the efficiency of the specimen fabrication to be furtherimproved.

FIG. 10 is a diagram showing a typical configuration for mounting theTEM-specimen holder 19 on the sample cassette 17. As shown in thefigure, on a TEM stage 87, the TEM-specimen holder 19 and peripheralsthereof are formed into a holder cartridge 88. A plurality of holdercartridges 88 are mounted on the sample cassette 17. In thisconfiguration, the TEM stage 87 is inserted from the outside of thevacuum chamber 77 through a side entrance and a desired holder cartridge88 is mounted on the TEM stage 87. The TEM stage 87 can then beintroduced into the TEM-specimen chamber with a holder cartridge mountedthereon as it is. In this way, by forming a TEM-specimen holder 19 andperipherals thereof of the TEM stage 87 into a holder cartridge 88, amicro-specimen 40 can now be mounted on a TEM with ease.

1-5 [Probe]

FIG. 11 is explanatory diagrams used for describing a typicalconfiguration of the probe 11. In particular, the figure shows a typicalconfiguration of a probe 11 exhibiting a spring effect. As shown in FIG.1l/(a), at a middle of a long and thin probe 11, a spring-structureportion 89 having a curved shape is provided. In this configuration,when the tip of the probe 11 is brought into contact with amicro-specimen formation area 2-1 on the surface of the specimensubstrate 2, an impact force generated between the probe 11 and themicro-specimen formation area 2-1 is absorbed by the spring-structureportion 89, preventing both the tip of the probe 11 and themicro-specimen formation area 2-1 from being injured. In addition, evenif the position of a probe holder 91 relative to a contact position 90changes subtly due to thermal drift or the like after the tip of theprobe 11 has been brought into contact with the micro-specimen formationarea 2-1, the contact position 90 can be sustained at a stable locationby a spring effect of the spring-structure,portion 89 as shown forexample in FIG. 11/(c).

By using a probe exhibiting a spring effect as described above, aninjury can be prevented from being inflicted upon both the probe 11 andthe micro-specimen 40. In addition, the posture of the probe 11 can becompensated for a change in position of the probe 11 relative to themicro-specimen 40 caused by thermal drift or the like.

1-6 [Means for Fixing the Tip of the Probe to a Micro-Specimen FormationArea and Separating Them from Each Other]

As a method for fixing the tip of the probe 11 to a portion on thespecimen substrate 2 to be created as a micro-specimen 40, a technologyof creating a deposition film by the IBAD method has been described. Onthe other hand, a technology of removing the deposition film by the IBSmethod is adopted as described earlier. Other methods for fixing the tipof the probe 11 to a micro-specimen formation area 2-1 and separatingthe probe 11 from the micro-specimen 40 are described as follows.

In place of the IBAD method using deposition gas described earlier, thetip of the probe 11 can also be firmly joined to a portion on thespecimen substrate 2 to be created as a micro-specimen 40 through a filmcreated by redeposition of ion-beam sputter particles emanating from thespecimen substrate 2 on the specimen substrate 2. Such a film isreferred to hereafter as a redeposition film. As a method to separatethe probe 11 from the micro-specimen 40, a technique of peeling off theredeposition film using the IBS method can be adopted. As analternative, the probe 11 can also be separated from the micro-specimen40 by cutting off the probe 11 by using the IBS method.

As another alternative, adhesive is applied to the surface of the tip ofthe probe 11 in advance and then, by merely bringing the tip of theprobe 11 into contact with a micro-specimen formation area 2-1, the tipof the probe 11 can be firmly joined to the micro-specimen formationarea 2-1. Unlike the a technique of using a deposition film by adoptionof the IBAD method described earlier, this other-alternative methodoffers a merit that the length of time it takes to carry out the work ofjoining the tip of the probe 11 to the micro-specimen formation area 2-1can be reduced. As the adhesive, it is possible to use UV-rayexfoliative adhesive, the sticking power of which can be reduced byirradiation of an ultraviolet ray thereto. If such adhesive is used, theprobe 11 can be separated from the micro-specimen 40 by using anultraviolet-ray radiating means. In this case, however, a capability ofradiating an ultraviolet ray to the contact portion is required as acondition. Thus, such adhesive can not be used under a condition whereinan ultraviolet ray is shielded. As an alternative, it is also possibleto use heating-exfoliative adhesive, the sticking power of which can bereduced by heat, as adhesive for sticking the tip of the probe 11 to themicro-specimen formation area 2-1. In this case, the probe 11 can beseparated from the micro-specimen 40 by using a heating means. In anexample shown in FIG. 12, an electricity path 92 is provided in thevicinity of the probe 11 for heating the probe 11 by Joule's heating toa temperature in the range 80 to 100 degrees Celsius. In this way, theheating-exfoliative adhesive can be peeled off with ease.

FIG. 13 is diagrams showing another example of a method of firmlyjoining the probe 11 to a micro-specimen 40. As a technique offabricating a specimen, the IBS method of using an ion beam 13, strictlyspeaking, a positive ion beam 13, is adopted. In this case, according tothe method shown in FIG. 13, the probe 11 is fixed to a micro-specimenformation area 2-1 and separated from a micro-specimen 40 by using anelectrostatic absorption technique. To put it in detail, first of all,the surface of the probe 11 is covered by an insulating material 93. Anelectric-potential difference is then applied between the probe 11 andthe micro-specimen formation area 2-1 to generate a force ofelectrostatic absorption for firmly joining the probe 11 to themicro-specimen formation area 2-1. This method has a merit of noaccompanying chemical change in quality and no accompanyingcontamination. Here, the reason why the micro-specimen formation area2-1 is charged with positive electric charge as shown in FIG. 13/(a) isto prevent the area 2-1 from being neutralized by the positive ion beam13. If a negative ion beam or an electron beam is irradiated, on theother hand, it is necessary to charge the micro-specimen formation area2-1 with negative electric charge instead. In this state, the tip of theprobe 11 can be firmly joined to the micro-specimen 40 as shown in FIG.13/(b). The micro-specimen 40 firmly joined to the tip of the probe 11is then conveyed to the TEM-specimen holder 19 to be fixed to themetallic wire 83 of the TEM-specimen holder 19. A method to fix themicro-specimen 40 to the metallic wire 83 will be described later. Afterthe micro-specimen 40 has been fixed to the metallic wire 83, the probe11 and the metallic wire 83 are short-circuited as shown in FIG. 13/(c)to neutralize the micro-specimen 40 from the electric charge chargedtherein. The neutralization of the electric charge allows the tip of theprobe 11 to be separated from the micro-specimen 40 as shown in FIG.13/(d).

As an alternative, the probe 11 is heated by using a Joule's heatingmethod, that is, a method similar to that shown in FIG. 12, or a heatingmethod by local laser irradiation. Then, the tip of the probe 11 isfixed to the micro-specimen formation area 2-1 by fusion caused by athermal reaction of the tip in contact with the micro-specimen formationarea 2-1. However, it is quite within the bounds of possibility that thehigh-temperature heating of the whole of the micro-specimen formationarea 2-1 changes the quality of the micro-specimen 40 itself. It is thusnecessary to locally heat the micro-specimen formation area 2-1 in ashort period of time.

As is generally known, by merely bringing 2 metals each having a cleansurface into contact with each other, a junction can be formed betweenthe two metals. Thus, for example, the tip of a metallic probe 11 madeof typically tungsten can be firmly joined to a contact portion of themicro-specimen formation area 2-1 as follows. First of all, theirsurfaces are each cleaned in a surface sputtering process by irradiationof an ion beam in a vacuum chamber. Then, the tip of the metallic probe11 is firmly joined to the contact portion of the micro-specimenformation area 2-1 through a metallic junction between them. Inaddition, a junction can be created by such surface cleaning between 2pieces of silicon. Thus, in the case of a silicon sample, the tip of theprobe 11 can be firmly joined to the micro-specimen formation area 2-1by the same process provided that the probe 11 is also made of silicon.

1-7 [Means for Fixing a Micro-Specimen to the TEM-Specimen Holder]

FIG. 14 is a diagram showing another example of a method to fix amicro-specimen 40 to the TEM-specimen holder 19. In this example, amicro-specimen 40 can be firmly joined to the TEM-specimen holder 19 byheating a contact portion between the micro-specimen 40 and theTEM-specimen holder 19. As shown in the figure, the fixed unit 84 of themetallic wire 83 employed in the TEM-specimen holder 19 is divided into2 portions and an insulator 94 is placed between these 2 portions. Byflowing a current between holder support electrodes 95 and 96, Joule'sheat is generated to raise the temperature of the metallic wire 83.Then, by bringing a fixed member of the micro-specimen 40 into contactwith the heated metallic wire 83, the fixed member of the micro-specimen40 can be firmly joined to the metallic wire 83 by fusion.

The micro-specimen 40 can also be firmly joined to the TEM-specimenholder 19 by the IBAD method using a deposition film or the IBS methodusing a redeposition film described earlier. When a micro-specimen 40 isfixed to the TEM-specimen holder 19 by using adhesive, unlike the casein which the tip of the probe 11 is joined to the micro-specimen 40 onlytemporarily, it is necessary to firmly fix the micro-specimen 40 to theTEM-specimen holder 19 in a stable state which lasts for a long periodof time, at least till an observation by using a TEM is completed. It isthus desirable to use adhesive that has a strong sticking power.

As another method of fixing the micro-specimen 40 to the TEM-specimenholder 19, the surfaces of a contact portion between the micro-specimen40 and the TEM-specimen holder 19 on both sides is cleaned to create ajunction between the micro-specimen 40 and the TEM-specimen holder 19 bybringing the surfaces into contact with each other. The surfaces canbe-cleaned by using typically an ion-sputter method.

1-8 [Extraction of a Micro-Specimen by Ion-Beam Fabrication]

In order to separate a micro-specimen 40 from a specimen substrate 2,the bottom-dividing process technology described earlier is required.

In a first method, an ion beam (PJIB) generated by a PJIB irradiatingoptical system is used as a fabrication beam as shown in FIG. 1. Thesample stage 3 is inclined so that the PJIB is irradiated to the surfaceof the specimen substrate 2 in a slanting direction with respect to thesurface in order to carry out a desired bottom-dividing fabrication.This first method is the same as the method explained earlier byreferring to FIG. 4 or the method explained thereafter by referring toFIG. 17.

In a second method, an ion beam (FIB) is used as a fabrication beam asshown in FIG. 5C. Much like the first method, the sample stage 3 isinclined so that the FIB is irradiated to (strictly speaking, driven ina scanning operation to sweep over) the surface of the specimensubstrate 2 in a slanting direction with respect to the surface in orderto carry out a bottom-dividing fabrication to extract a micro-specimen40.

According to a third method, there are provided a first PJIB irradiatingoptical system 1 (column I) for making a trench with perpendicular sidewalls on the surface of the specimen substrate 2 and a second PJIBirradiating optical system 97 (column II) which is oriented in aslanting direction and used for performing the bottom-dividingfabrication described above as shown in FIG. 15. To be more specific,column II is used for carrying out a desired bottom-dividingfabrication. As column II oriented in a slanting direction, an FIBirradiating optical system can be employed in place of a PJIBirradiating optical system.

A fourth method shown in FIG. 16 is a bottom-dividing method that doesnot use an ion beam. As shown in FIG. 16/(a), first of all, trenches 98are created around a desired observation area on the surface of thespecimen substrate 2 by ion-beam fabrication to form a protrudingmicro-specimen formation portion 99. Then, a wedge 100 is inserted intothe trench 98 on one side of the micro-specimen formation portion 99 toseparate a micro-specimen 40 by a shearing force. In comparison with thebottom-dividing fabrication methods using an ion beam as describedabove, the fourth method has a merit that the bottom-dividingfabrication can be completed in a short period of time. In order to makethe separation by a shearing force easy to accomplish, the trenches 98are created around a micro-specimen formation portion 99 in such aslightly slanting direction that the more we look into the inner side ofthe specimen substrate 2, the thinner the cross section of themicro-specimen formation portion 99 as shown in FIG. 16/(b). As analternative, an infinitesimal plate 102 attached to a piezoelectricdevice 101 is inserted into the inside of the trench 98 as shown in FIG.16/(c). Then, by actuating the piezoelectric device 101, a force isapplied to the micro-specimen formation portion 99 in the transversaldirection, separating a micro-specimen 40 by shearing.

By carrying out a bottom-dividing fabrication as described above, aninfinitesimal micro-specimen 40 with a small depth can be created on theupper portion of the specimen substrate 2. As a result, the fabricationcan be completed in a shorter period of time. In particular, by adoptingthe shearing separation method in the bottom-dividing fabrication, amicro-specimen 40 can be separated and extracted at a high speed.

Second Embodiment

FIG. 17 is process explanatory diagrams showing another embodiment ofthe present invention for implementing a method for fabrication of a TEMspecimen. The method is adopted in the specimen fabrication apparatusshown in FIG. 1 and only a PJIB is used as an ion beam for fabrication.

First of all, a PJIB 13′ is irradiated to regions surrounding anobservation area 103 on the specimen substrate 2 shown in FIG. 17/(a) byusing a mask with a shape resembling a symbol ‘]’ as shown in FIG.17/(b) to form a trench 104 having a bottom with a shape resembling the‘]’ symbol as shown in FIG. 17/(c). Then, the sample stage 3 shown inFIG. 1 is inclined to carry out a bottom-dividing fabrication by meansof the PJIB 13′ as shown in FIG. 17/(d). Subsequently, the tip of theprobe 11 held by the probe driver 4 is brought into contact with amicro-specimen formation portion 99. The state of contact between thetip of the probe 11 and the micro-specimen formation portion 99 can beverified by detection of, among other phenomena, a variation in contactresistance between the probe 11 and the specimen substrate 2, that is,the micro-specimen formation portion 99, or a variation in voltagecontrast on a secondary-electron image. The tip of the probe 11 broughtinto contact with the micro-specimen formation portion 99 is then firmlyjoined to the micro-specimen formation portion 99 by using a depositionfilm created by adoption of the IBAD method as shown in FIG. 17/(e).Then, a micro-specimen 40 is cut out from the specimen substrate 2 byirradiating the ion beam PJIB 13′ to the remaining sides of themicro-specimen 40 as shown in FIG. 17/(f). The fact that the probe 11,that is, the micro-specimen 40, has been separated from the specimensubstrate 2 is verified by detection of, among other phenomena, anincrease in contact resistance between the probe 11 and the specimensubstrate 2 or a variation in voltage contrast on a secondary-electronimage. The micro-specimen 40 separated from the specimen substrate 2 isthen conveyed to the TEM-specimen holder 19 by the probe driver 4 asshown in FIG. 17/(g). Subsequently, the micro-specimen 40 separated fromthe specimen substrate 2 is brought into contact with the metallic wire83 of the TEM-specimen holder 19 as shown in FIG. 17/(h). The state ofcontact between the micro-specimen 40 firmly joined to the probe 11 andthe metallic wire 83 of the TEM-specimen holder 19 is verified bydetection of a decrease in contact resistance between the probe 11, thatis, the micro-specimen 40, and the TEM-specimen holder 19, that is, themetallic wire 83, or a variation in voltage contrast on asecondary-electron image. After the micro-specimen 40 has been broughtinto contact with the metallic wire 83, the former is firmly joined tothe latter by using a deposition film created by adoption of the IBADmethod. After the micro-specimen 40 has been firmly joined to themetallic wire 83, a PJIB or an FIB is irradiated to a contact portionbetween the tip of the probe 11 and the micro-specimen 40 to carry out asputtering fabrication for separating the tip of the probe 11 from themicro-specimen 40 as shown in FIG. 17/(i). The fact that the tip of theprobe 11 has been separated from the micro-specimen 40 is by detectionof an increase in contact resistance between the probe 11 and themetallic wire 83 or a variation in voltage contrast on asecondary-electron image. Finally, the PJIB or the FIB is againirradiated to the micro-specimen 40 to carry out a thinning finishingprocess to thin the observation area 103 to a final thickness of about100 nm or smaller in order to produce a TEM specimen as shown in FIG.17/(j).

As described above, this embodiment is exemplified by a method forfabrication of a specimen subjected to an observation using a TEM. Itshould be noted that, of course, this method can be adopted forfabrication of a specimen for other types of observation, a specimen foranalyses and a specimen for measurements. In this case, the finishingprocess for thinning the area to be observed shown in FIG. 17/(j) is notnecessarily required.

Methods for fabrication of a specimen provided by the present inventionare not limited to the embodiments described above. It is needless tosay that other apparatuses and technological means can be combined. Forexample, in the process of carrying out a bottom-dividing fabricationshown in FIG. 17/(d), any of the 4 methods described above can beadopted. The method for firmly joining the tip of the probe 11 to amicro-specimen formation portion 99 and the method for separating thetip of the probe 11 from a micro-specimen 40 can be replaced by theother methods described above. In addition, the shape of the PJIB 13′used for formation of a micro-specimen 40 is not limited to the shaperesembling the ‘]’ symbol used in the embodiment described above. Forexample, a combination of a plurality of PJIB projections each having arectangular pattern can be adopted to produce a similar pattern offabrication. As an alternative, a PJIB with a rectangular pattern ismoved in a scanning operation to sweep the surface of the specimensubstrate 2 to produce a desired pattern. In addition, an FIB can beused in place of a PJIB. Furthermore, a PJIB irradiating optical system1 can be employed in an apparatus for fabrication of a specimen inconjunction with an FIB irradiating optical system 1 so that either ofthe optical systems can be selected in dependence of the purpose of thefabrication. Last but not least, the ion-beam sputtering fabricationmethod can be adopted in conjunction with the laser-beam fabricationmethod to carry out the separation fabrication.

Third Embodiment

FIG. 18 is process explanatory diagrams showing a further otherembodiment of the present invention for implementing a method forfabrication of a TEM specimen. In this embodiment, a marking process forclarifying a specific position 105 on a micro-specimen 40 to be observedor analyzed is added to the methods for fabrication the micro-specimen40 described earlier. It should be noted that, since the other processesin this third embodiment are virtually the same as those shown in FIG.17, their explanation with reference to diagrams is not repeated. Inthis embodiment, in order to avoid the observation location 105 frombeing no longer unidentifiable after the micro-specimen 40 including aspecific location 105 to be observed has been extracted from thespecimen substrate 2, a process to put a mark on the observationlocation 105 is added in order to clearly show the observation location105. The observation location 105 is a specific location at which a thinwall portion for observations by using a TEM is to be created. When thespecimen substrate 2 is still in a wafer or chip state prior to thespecimen fabrication, a position on the specimen substrate 2 can befound from information such as CAD data. That is why a mark is put onthe observation location (the thin-wall formation location) 105 prior tothe fabrication to extract the micro-specimen 40. In the markingprocess, cross marks 106 and 107 are typically put on both the ends ofthe observation location 105 by fabrication using an ion beam or thelike as shown in FIG. 18/(a). The cross marks 106 and 107 allow theobservation location 105 to be recognized clearly as shown in FIG.18/(b) even after the micro-specimen 40 has been extracted from thespecimen substrate 2. Then, a thin wall is formed by leaving a portioncoinciding with a straight line connecting the marks 106 and 107 to eachother, that is, the observation location 105 as shown in FIG. 18/(c). Asa result, a cross section at a desired location can be observed. Asdescribed above, by virtue of the additional marking process, a locationto be observed can be identified with a high degree of accuracy evenafter an infinitesimal micro-specimen 40 has been created. It should benoted that, in order to protect the observation location 105, adeposition film is created in advance on the surface of themicro-specimen 40 prior to the marking process.

Fourth Embodiment

FIG. 19 is a diagram showing a configuration of the basic specimenfabrication apparatus as implemented by another embodiment of thepresent invention in a simple and plain manner. As shown in the figure,the specimen fabrication apparatus implemented by this embodimentcomprises at least:

a movable sample stage 3 on which a specimen substrate 2 is mounted;

an FIB (focused ion beam) irradiating optical system 1 for irradiating afocused ion beam (FIB) 13 to the surface of the specimen substrate 2;

a secondary-particle detector 12 for detecting secondary particles suchas secondary electrons and secondary ions emitted by the surface of thespecimen substrate 2 due to irradiation of the FIB 13 to the surface;

a deposition-gas supplying source 8 for supplying deposition gas, thatis, gas used for formation of a deposition film, to an area on thesurface of the specimen substrate 2 to which the FIB 13 is irradiated;

a TEM-specimen holder 19′ for firmly holding a micro-specimen 40extracted from the specimen substrate 2;

a holder cassette 17′ for holding the TEM-specimen holder 19′; and

a specimen transferring unit 4 for transferring the micro-specimen 40extracted and separated from the specimen substrate 2 to theTEM-specimen holder 19′.

In addition, the specimen fabrication apparatus also includes:

a sample-stage position controller 3′ for controlling the position ofthe sample stage 3;

a deposition-gas supplying source controller 8′ for controlling thedeposition-gas supplying source 8;

a specimen transferring unit controller 4′ for controlling and drivingthe specimen transferring unit 4 independently of the sample stage 3;

an image display sub-unit 5 for displaying, among other things, imagesof the surface of the specimen substrate 2, the surface of theTEM-specimen holder 19′ and the tip of a probe 11 held by the specimentransferring unit 4; and

an FIB controller 7 for driving and controlling the FIB irradiatingoptical system 1.

It should be noted that the sample-stage position controller 3′, thespecimen transferring unit controller 4′, the image display sub-unit 5,the FIB controller 7, the deposition-gas supplying source controller 8′and some other components are controlled by a central processing unit(CPU) 6.

As shown in FIG. 19, the FIB irradiating optical system 1 lets an ionbeam emitted by a liquid metallic ion source 41 pass through a beamlimiting aperture 42, a condenser lens 49 and an objective lens 50 toproduce a focused ion beam (FIB) 13 with a diameter in the range severaltens of nmφ to about 1 μmφ. The FIB 13 is driven by a deflector 51 in ascanning operation carried to sweep the surface of the specimensubstrate 2, allowing fabrication to be carried out on the surface inaccordance with the shape of a scanning pattern at a precision in therange 1 micron to a value at a sub-micron level. Here, what are meant bythe technical term ‘fabrication’ include formation of a dent bysputtering, formation of a protrusion by ion-beam assist deposition(IBAD) and a fabricating operation such as modification of the shape ofthe specimen substrate surface through a combination of the formation ofdents and the formation of protrusions. A deposition film (IBAD film)created by irradiation of the FIB 13 is used for firmly joining the tipof the probe 11 held by the specimen transferring unit 4 to the surfaceof the specimen substrate 2 and a micro-specimen 40 extracted from thespecimen substrate 2 to the TEM-specimen holder 19′. Thesecondary-particle detector 12 is used for detecting secondary particlessuch as secondary electrons and secondary ions emitted by the surface ofthe specimen substrate 2 due to irradiation of the FIB 13 to thesurface. A detection signal generated by the secondary-particle detector12 creates an image of a portion to which the FIB 13 is irradiated and,by displaying the image, the portion such as a fabricated area can beobserved. The sample stage 3 is placed in the sample chamber 77 andcomponents such as the FIB irradiating optical system 1 are located in avacuum container. A holder cassette 17′ for holding the TEM-specimenholder 19′ can be mounted on and removed from the sample stage 3. Thesample stage 3 is designed so that the stage 3 can be moved in thethree-dimensional directions, namely, the X, Y and Z axial directions,can be tilted and can be rotated. The sample-stage position controller3′ is used for controlling the position of the sample stage 3.

Configurations and functions of elements constituting the specimenfabrication apparatus as implemented by the fourth embodiment of thepresent invention are described in concrete terms and in more detail asfollows.

4-1 [Specimen Transferring Unit and Its Place of Installation]

FIG. 20A is a diagram showing a typical configuration of the specimentransferring unit 4 for transferring a micro-specimen 40 extracted fromthe specimen substrate 2 to the TEM-specimen holder 19′. As shown in thefigure, the specimen transferring unit 4 comprises 2 units, namely, acoarse-movement actuator 56 and a fine-movement actuator 55. Composed ofelectro-mechanical components such a motor, a gear and a piezoelectricdevice, an XYZ-direction driving mechanism of the coarse-movementactuator 56 has a movement range (stroke) of at least 3 mm with amovement resolution of the order of several microns. Required of ascompact a design as possible, the fine-movement actuator 56 employs apiezoelectric device. Particularly, in the case of this embodiment, abimorph-type piezoelectric device is selected. The bimorph-typepiezoelectric device offers a merit of a relatively long stroke of atleast several hundreds of microns in comparison with piezoelectricdevices of other types. On the other hand, since the coarse-movementactuator 56 is not required of a high positional precision, thecoarse-movement actuator 56 can be manufactured with ease. Thecoarse-movement actuator 56 employed in this embodiment vibrates at anamplitude in a range of ten plus several microns during a movement, butthe vibration is all but negligible in a stationary state. Thus, it ispossible to adopt a method whereby the tip of the probe 11 is firsttaken to a position in close proximity to the surface of the specimensubstrate 2 and put at a standstill by using the coarse-movementactuator 56 before the tip of the probe 11 is brought into contact withthe surface of the specimen substrate 2 by means of the fine-movementactuator 55. With this method, since a resolution of the order ofmicrons will prove sufficient for positional control of the tip of theprobe 11, even the bimorph-type piezoelectric device having a relativelypoor resolution in comparison with piezoelectric devices of other typesis capable of satisfactorily satisfying the requirement of thepositional control. As a result, the fine-movement actuator 55 can bemanufactured at a low cost.

As described previously, with the conventional technology disclosed inJapanese Patent Laid-open No. Hei 5-52721 used as prior-art reference 3,a manipulator serving as a unit for conveying a micro-specimen 20extracted from the specimen substrate 2 has a configuration including 3bimorph-type piezoelectric devices for movements in the X, Y and Z axialdirections respectively. Since this conveying unit is installed on thesample stage 3 on which the specimen substrate 2 is mounted, however,there is raised a fatal problem that, in the case of an area to beobserved existing at the center of the specimen substrate (wafer) havinga large diameter of 300 mm, the movement stroke of the conveying unit isnot sufficient for the tip of the probe 11 to reach the area. Inaddition, as described above, the conveying means employs 3 bimorph-typepiezoelectric devices for movements in the X, Y and Z axial directionsrespectively wherein each of the bimorph-type piezoelectric devices hasone end thereof serving as a fixed supporting point and the other endmoving to bend the device. That is, the other end moves along anarc-shaped locus in accordance with an applied voltage. Strictlyspeaking, in a movement on the XY plane, driven only by a specificbimorph-type piezoelectric device, the tip of the probe does not move inan axial direction corresponding to the specific bimorph-typepiezoelectric device along a truly straight line. Thus, with thefine-movement actuator 55 comprising the 3 bimorph-type piezoelectricdevices, in order to move the tip of the probe 11 to a desired locationwith a high degree accuracy, it is necessary to move each of the 3bimorph-type piezoelectric devices by taking the movements of the othersinto consideration. As a result, there is raised a problem of complexoperations to drive the 3 bimorph-type piezoelectric devices in such amanner that their movements are related to each other. In order to solvethis problem, it is necessary to employ 3 axial-direction driving meansthat are each capable of moving the probe 11 along a straight line witha high degree of accuracy. If the conveying unit is required to becapable of moving the probe 11 by a long stroke of at least 100 mm aswell as a resolution of the micron order by utilizing only afine-movement mechanism, the structure of the mechanism will becomecomplicated and will become big in size. As a result, a problem ofcontention for installation space with other components surrounding thesample stage 3 such as the secondary-electron detector 12 and thedeposition-gas supplying source 8 will remain to be solved.

In order to solve the problems described above, the present inventionprovides a specimen transferring unit 4 that is capable of carrying outsampling quickly from any arbitrary location even if the specimensubstrate 2 is a wafer with a large diameter. In order to realize such acapability, the specimen transferring unit 4 is designed to comprise acoarse-movement actuator 56 having a high movement speed and a largestroke and a fine-movement actuator 55 having a stroke about equal tothe movement resolution of the coarse-movement actuator 56 and a highmovement resolution. In addition, the whole specimen transferring unit 4is installed independently of the sample stage 3 and a movement over along distance to a sampling position is made by partly resorting to amovement by the sample stage 3. Furthermore, the coarse-movementactuator 56 which has a tendency to increase in size is provided at alocation very far away from the specimen substrate 2 and thefine-movement actuator 55 is implemented by a fine-movement mechanismfor movements in the Z-axial direction only. As a result, interferencein space of installation with other components surrounding the samplestage 3 can be avoided. As described above, the specimen transferringunit 4 provided by the present invention is designed by sufficientlytaking the size and the place to install into consideration. As aresult, the specimen transferring unit 4 solves all the problemseffectively.

As shown in the FIG. 20A, in the configuration of the coarse-movementactuator 56, a coarse-movement shaft 59 is moved in the X, Y and Z axialdirections by encoders 28X, 28Y and 28Z respectively with an isthmus 63used as a supporting point. It should be noted that the encoder 28Y isnot shown in the figure. While the coarse-movement stroke and themovement resolution are dependent on the performance of each of theencoders 28X, 28Y and 28Z, a stroke of 10 mm and a resolution of 2microns can be achieved with ease. A force for resisting a pressingforce generated by each of the encoders 28X, 28Y and 28Z is provided bya means such as a spring. The generation of such a resisting force isnot explained in this description. A driving system of thecoarse-movement actuator 56 is provided on the atmosphere side through aside port 54′ of a specimen chamber 54. A vacuum state of the specimenchamber 54 is shielded against the atmosphere by a bellows 64. A portionof the coarse-movement shaft 59 on the vacuum-chamber side is linked tothe fine-movement actuator 55 through an extension rod 30. Thefine-movement actuator 55 is designed to drive the probe 11 only in theZ-axial direction. In a driving system of the fine-coarse actuator 56, abimorph-type piezoelectric device 29 is employed to provide a movementresolution of the sub-micron order. The end of the bimorph-typepiezoelectric device 29 is joined to a probe 11 made of a tungsten wirewith a pointed tip having a diameter of 50 μmφ. When a driving voltageis applied to the bimorph-type piezoelectric device 29, the tip of theprobe 11 makes a fine movement.

FIG. 20B is a diagram showing another example of the configuration ofthe specimen transferring unit 4. In this example, the configuration ofthe coarse-movement actuator 56 comprises a combination of 3block-shaped piezoelectric devices 73, 74 and 75 for movements in the X,Y and Z axial directions respectively. A block-shaped piezoelectricdevice has a slightly inferior movement resolution but offers meritssuch as a long movement stroke and endurance against a heavy load. Thecoarse-movement actuator 56 is connected to a fine-movement actuator 55implemented by a bimorph-type piezoelectric device 72′ through anextension rod 71′. The fine-movement actuator 55 is used for holding theprobe 11.

A typical case in which the specimen transferring unit 4 shown in FIG.20B is installed in the specimen chamber 54 is shown in FIG. 20C. Inthis example, a small vacuum chamber 54″ is provided through the sideport 54′ of the specimen chamber 54. In the small vacuum chamber 54″,the coarse-movement actuator 56 is installed. When the specimentransferring unit 4 is not in use, it can be taken out with ease fromthe specimen chamber 54 by using a slider 111 which can be sled along arail 110. In this configuration, the only components placed inside thespecimen chamber 54 are the extension rod 71′, the bimorph-typepiezoelectric 72′ attached to the end of the extension rod 71′ and theprobe 11. Thus, interference with a variety of other components in thespecimen chamber 54 can be avoided, allowing the probe 11 to make anaccess to the surface of the specimen substrate 2.

FIG. 21 is explanatory diagrams each showing a location at which thespecimen transferring unit 4 is installed. To be more specific, FIG.21/(a) is a diagram showing an example wherein the specimen transferringunit 4 comprising the coarse-movement actuator 56 and the fine-movementactuator 55 is attached to a side wall 54 of the specimen chamber 77 insuch a way that the probe 11 is capable of making an access to aposition between the surface of the specimen substrate 2 mounted on thesample stage 3 and a final electrode 112 of the FIB irradiating opticalsystem 1 which is installed to face the surface of the specimensubstrate 2. On the other hand, FIG. 21/(b) is a diagram showing anexample wherein the specimen transferring unit 4 is installed on theceiling 54A of the specimen chamber 77. Finally, FIG. 21/(c) is adiagram showing an example wherein the specimen transferring unit 4 isinstalled on a side surface of a final electrode 112 of the FIBirradiating optical system 1. A point common to these examples is thefact that, in the configurations, the specimen transferring unit 4 isnot placed on the sample stage 3 and driven as well controlledindependently of the sample stage 3. As such, the configurations aredesigned in such a way that, during a movement of the specimen substrate2, the specimen transferring unit 4 never comes in contact with thesurface of the specimen substrate 2.

In the configuration shown in FIG. 21/(a), the specimen transferringunit 4 is attached to the side wall 54 of the specimen chamber 77 sothat the specimen transferring unit 4 is capable of keeping up with anapparatus without a side port provided on the side wall 54 of thespecimen chamber 77. In the example shown in FIG. 21/(b), on the otherhand, the specimen transferring unit 4 is installed on the ceiling 54Aof the specimen chamber 77, offering merits that the space in thespecimen chamber 77 can be utilized effectively and the specimentransferring unit 4 is capable of keeping up with apparatuses eachhaving a different configuration. Finally, in the configuration shown inFIG. 21/(c), the specimen transferring unit 4 is installed on a sidesurface of the final electrode 112 of the FIB irradiating optical system1, also offering merits that the space in the specimen chamber 77 can beutilized effectively and no excessive components protrude out to theoutside of the specimen chamber 77. As a result, the outside of thespecimen chamber 77 can be occupied by other components with complicatedconfigurations and the external view of the apparatus can be made lookclean.

A variety of other configurations for installing the specimentransferring unit 4 are possible. At any rate, the basic conceptembraced in the examples of the configurations shown in FIG. 21 is toinstall the specimen transferring unit 4 in such a way that the specimentransferring unit 4 can be driven as well controlled independently ofthe sample stage 3 and, during a movement of sample stage 3, thespecimen transferring unit 4 never comes in contact with the surface ofthe specimen substrate 2. As a result, an access can be made to anymicro-specimen 40 to be extracted with ease even if the micro-specimen40 is located at the center of a wafer having a large diameter.

4-2 [Locations for Installing the TEM-Specimen Holder]

A micro-specimen 40 extracted from the specimen substrate 2 istransferred to the TEM-specimen holder 19′ serving as a member to whichthe micro-specimen 40 is to be fixed. In order to transfer amicro-specimen 40 to the TEM-specimen holder 19′, it is necessary tomount the TEM-specimen holder 19′ on the sample stage 3 by using theholder cassette 17′ for holding the TEM-specimen holder 19′ or to mountthe TEM-specimen holder 19′ on a side-entry-type stage such as a TEMstage which is independent of the sample stage 3. The sample stage 3 canbe a general-purpose large-size sample stage allowing a wafer itself tobe mounted thereon or a sample stage with a small size enough formounting a device chip. A place at which the specimen holder 19′ isinstalled greatly affects the workability following an operation totransfer a micro-specimen 40 extracted from the specimen substrate 2 tothe TEM-specimen holder 19′. For this reason, a place at which thespecimen holder 19′ is installed is explained specially as follows.

The following description explains 3 systems to install the TEM-specimenholder 19′, namely, a sample-stage system, a wafer-cassette system and aTEM-stage system. In the sample-stage system, the TEM-specimen holder19′ is mounted on the sample stage 3. In the wafer-cassette system, onthe other hand, the TEM-specimen holder 19′ is mounted on a wafercassette which accommodates the specimen substrate 2 (that is, thewafer) and can be put in and taken out from the specimen chamber 77.Finally, in the TEM-stage system, the TEM-specimen holder 19′ is mountedon a TEM stage (or a stage for both the TEM and the FIB).

4-2-1 [Sample-Stage System]

FIG. 22 is explanatory diagrams showing an example of a method toinstall the TEM-specimen holder 19′ in the sample-stage system. To bemore specific, FIG. 22/(a) is a diagram showing a top view of the samplestage 3 and FIG. 22/(b) shows a cross section of the center of thesample stage 3. In this system, the TEM-specimen holder 19′ is set onthe holder cassette 17′ which can be mounted on and removed from thesample stage 3 with ease. The number of TEM-specimen holders 19′ thatcan be set on the holder cassette 17′ is arbitrary and the number ofholder cassettes 17′ that can be mounted on the sample stage 3 is alsoarbitrary. FIG. 22/(a) shows an example in which 1 holder cassette 17′is mounted on the sample stage 3 and 5 TEM-specimen holders 19′ are setin the holder cassette 17′. If 3 micro-specimens 40 extracted from thespecimen substrate 2 are mounted on each of the TEM-specimen holders19′, 15 TEM specimens can be mounted on the holder cassette 17′.

The holder cassette 17′ is mounted on the sample stage 3 in such a waythat the upper surface of the TEM-specimen holder 19′ is set at aboutthe same level as the surface of the specimen substrate 2. In this way,when a micro-specimen 40 extracted from the specimen substrate 2 istransferred to the TEM-specimen holder 19′, the micro-specimen 40 doesnot come in contact with the TEM-specimen holder 19′ and othercomponents. Furthermore, the desired surface on the micro-specimen 40 tobe observed is oriented in a direction parallel to the longitudinaldirection of the TEM-specimen holder 19′ which is set in such a way thatthe longitudinal direction thereof is parallel to an inclination axis113 of the sample stage 3. It should be noted that the shape of theTEM-specimen holder 19′ will be described later in concrete terms. Sucha positional arrangement allows the micro-specimen 40 extracted from thespecimen substrate 2 to be mounted on the TEM-specimen holder 19′ in amovement in the Z-axial direction only without the need to carry out anoperation on the micro-specimen 40 such as a rotation. Then, by mountingthe TEM-specimen holder 19′ with the extracted micro-specimen 40 mountedthereon on a TEM or SEM stage, the desired observation area can beobserved with ease.

The holder cassette 17′ can be mounted on or removed from the samplestage 3 by a sliding movement and, by using an operation rod, a loadlock chamber and other tools, the holder cassette 17′ can be taken outfrom the specimen chamber 77 without destroying the vacuum state of thespecimen chamber 77 in a manner independent of the sample stage 3. Byvirtue of this system, a large number of TEM micro-specimens 40 can befabricated continually from a specimen substrate 2 and, when the holdercassette 17′ is taken out from the specimen chamber 77, the same numberof TEM micro-specimens 40 can be obtained at once. In addition, the TEMmicro-specimens 40 mounted on TEM-specimen holders 19′ can betemporarily kept in a box for storage for each holder cassette 17′ inwhich the TEM-specimen holders 19′ are set. Thus, the work to handlethese infinitesimal TEM micro-specimens 40 is not a great strain on thenerves. In addition, the holder cassette 17′, on which a large number ofmicro-specimens 40 just extracted from the specimen substrate 2 as theyare and supposed to undergo a thinning fabrication or a wall fabricationare mounted, can be conveyed into a separately provided FIB apparatusserving as an apparatus used specially for carrying out the finishingfabrication (or the thinning fabrication) only.

A position on the sample stage 3 at which the TEM-specimen holder 19′ ismounted is explained by referring to FIG. 22/(b). Supposed to undergo afabrication such as the thinning fabrication described above, anextracted micro-specimen 40 has to be inclined. Thus, if the samplestage 3 is installed at an inappropriate location, there will be raiseda problem of a damage inflicted on the specimen transferring unit 4,making it impossible to fabricate the required micro-specimen 40.Components such as the holder cassette 17′ with TEM-specimen holder 19′set therein, the secondary-electron detector 12 and the deposition-gassupplying source 8 are always installed on a side on which the specimentransferring unit 4 is provided. In the example shown in FIG. 22/(b),the components are installed on the left-hand side of the sample stage 3with respect to the inclination axis 113. The inclination of the samplestage 3 causes the side on which the TEM-specimen holder 19′ is set,that is, the left side, to always move from a horizontal posture in adownward direction. As a result, interference with other structures inthe specimen chamber 77 described above can be avoided.

As another method regarding a place to install the TEM-specimen holder19′, it is possible to adopt a method whereby the structure of an end120 of a TEM stage 114 including a fixed portion of the TEM-specimenholder 19′ is improved and the TEM stage 114 is mounted on the samplestage 3. The following description begins with an explanation of the TEMstage 114 with a configuration allowing the end 120 thereof to beattached and detached. FIG. 23/(a) is a diagram showing the TEM stage114 used in this embodiment. As shown in the figure, the TEM stage 114comprises components such as a shaft 115, a handle 116, a positionsetting part 117 and a specimen fixing part 118. The TEM-specimen holder19′ is seated on a cut 123 of the shaft 115. The TEM stage 114 is mostcharacterized in that the stage 114 has a configuration that allows anend 120 thereof to be stuck to or detached from the main body of the TEMstage 114 at a separation position 119 as shown in FIG. 23/(b). That is,the end 120 can be detached from the main body and inserted into thesample stage 3. FIG. 23/(c) is a diagram showing a state in which theend 120 of the TEM stage 114 has been inserted into the sample stage 3.To put it in detail, the end 120 of the TEM stage 114 is inserted intoan insertion area 121 provided on the sample stage 3 to be held therein.The insertion area 121 has an opening 122 above the TEM-specimen holder19′. A micro-specimen 40 extracted from an area 124 to be observed onthe specimen substrate 2 is held on the tip of the probe 11 of thespecimen transferring unit 4 and transferred to the insertion area 121to be firmly held on the TEM-sample holder 19′ through the opening 122.

After the extracted micro-specimen 40 has been firmly held by theTEM-specimen holder 19′, the micro-specimen 40 is subjected to athinning fabrication (or a wall fabrication) by using an FIB with themicro-specimen 40 firmly held by the TEM-specimen holder 19′ as it is tobe converted into a TEM specimen. During the thinning fabrication, theFIB used for the fabrication is irradiated to the micro-specimen 40 in adirection perpendicular to the sheet of paper showing FIG. 23/(c).

Later on, when the micro-specimen 40 firmly held by the TEM-specimenholder 19′ is taken out from the specimen chamber 77, the main body ofthe TEM stage 114 is inserted into the insertion area 121 to join themain body to the end 120 of the TEM stage 114 in the insertion area 121.Then, the micro-specimen 40 is taken out from the specimen chamber 77along with the whole TEM stage 114. Held by the TEM stage 114, themicro-specimen 40 is brought into a TEM-specimen chamber to undergo anobservation using a TEM. During the observation using a TEM, an electronbeam used for the observation is irradiated to the micro-specimen 40 ina direction perpendicular to the sheet of paper showing FIG. 23/(a).

In the method described above by referring to FIG. 23, the end 120 ofthe TEM stage 114 which can be attached to and detached from the mainbody of the TEM stage 114 has a size of the cm order. Thus, the work toattach and detach the end 120 from the main body is not a great strainon the nerves. As a result, this method offers a merit that any personcan do the work to fabricate a TEM specimen with ease.

FIG. 24 is diagrams showing a further other example of a method toinstall the TEM-specimen holder 19′ on a TEM stage 114′ having astructure different from the TEM stage 114 described above. As shownFIG. 24/(a), the TEM stage 114′ comprises components such as a shaft115′, a handle 116′, a position setting part 117′ and a specimen fixingpart 118′. Unlike the method of installation shown in FIG. 23/(a),however, since no cut 123 is provided on the shaft 115′, the observationby using a TEM can not be carried out by using the same TEM stage 114′as the fabrication using an FIB. In order to solve this problem, the TEMstage 114′ is designed into a configuration that allows ends 120′ and120″ thereof to be stuck to or detached from the main body of the TEMstage 114′ at separation positions 119′ and 119″ respectively as shownin FIG. 24/(b). In FIG. 24, (a) and (b) are diagrams each showing astate in which no TEM micro-specimen 40 is fixed on the specimen fixingpart 118′. A plurality of ends 120′ each having no micro-specimen 40attached thereto are fixed to the sample stage 3 perpendicularly to thesurface of the sample stage 3, that is, the surface of the wafer formounting such ends 120′, in such a way that, after a TEM micro-specimen40 is seated on the TEM-specimen holder 19′, the TEM-observation surfaceis set in parallel to the inclination axis 113 of the sample stage 3 asshown in FIG. 24/(c). A micro-specimen 40 extracted from an area 124 onthe sample substrate 2 to be observed is held on the tip of the probe 11employed in the specimen transferring unit 4 and transferred to theTEM-specimen holder 19′ on the end 120′ of the TEM stage 114 which hasbeen firmly held on the sample stage 3 to be fixed to the TEM-specimenholder 19′. In the example shown in FIG. 24/(c), 7 TEM-specimen holders19′ are mounted on the sample stage 3. If 3 extracted micro-specimens 40are fixed on each of the TEM-specimen holders 19′, a total of 21 TEMspecimens 40 can be fabricated continually in the same specimen chamber.

4-2-2 [Wafer-Cassette System]

FIG. 25 is a diagram showing a typical configuration of an apparatusused in the wafer-cassette system. As shown in the figure, in thissystem, the holder cassette 17′ for holding the TEM-specimen holder 19′is mounted on a wafer cassette 125. Since the wafer cassette 125 is atray used exclusively for accommodating 1 wafer 2, that is, 1 specimensubstrate 2, components of the apparatus and the hands of the operatornever come in contact with the wafer 2 accommodated therein. Inaddition, since the wafer cassette 125 can be put in or taken out fromvarious kinds of process equipment as it is, the cassette 125 can alsobe used for transferring the wafer 2 from equipment to equipment. Asshown in FIG. 25, the holder cassette 17′ is designed into such aconfiguration that the holder cassette 17′ can be mounted on and removedfrom the holder-cassette mounting unit 121′ of the wafer cassette 125.Thus, a plurality of TEM-specimen holders 19′ each for mounting aplurality of TEM micro-specimens 40 can be obtained at the time thewafer 2 is replaced. A relation between the wafer cassette 125 and theholder cassette 17′, relations between the holder cassette 17′ andTEM-specimen holders 19′ set therein and relations between each of theTEM-specimen holders 19′ and extracted micro-specimens 40 fixed theretoare always controlled. As a result, it is easy to obtain informationsuch as a relation between a position on the wafer 2 from which a TEMmicro-specimen 40 has been extracted and information obtained as aresult of an analysis, a measurement or an observation using a TEM.

4-2-3 [TEM-Stage System]

In this system, a TEM-specimen holder 19′ is mounted on a stage whichoperates independently of the sample stage 3. By independently operatingstage, a TEM stage of the side-entry side type is typically implied. Inthis example, the side-entry-type TEM stage is designed into aconfiguration that can be put in or taken out from the specimen chamber77. In this case, the side-entry-type TEM stage is set so that an axisof rotation thereof is parallel to the inclination axis 113 of thesample stage 3. Note that it is desirable to place a desired area to beobserved as an extracted micro-specimen 40 on the rotation axis of theside-entry-type TEM stage. Since the extracted micro-specimen 40 to bemounted on the TEM-specimen holder 19′ has an infinitesimal size in therange several microns to 30 microns, however, in actuality, it issufficient to place the desired area at such a location that thespecimen fixing surface of the TEM-specimen holder 19′ comes to aposition close to the rotation axis of the side-entry-type TEM stage. Inthis configuration, a micro-specimen 40 extracted from the specimensubstrate 2 can be mounted on a TEM-specimen holder 19′ by only amovement in the Z-axial direction without the need to carry out anoperation such as a rotation. Thus, it is no longer necessary to add acomplex mechanism such as a tilting mechanism or a rotating mechanism tothe specimen transferring unit 4, giving rise to a merit of a simpleconfiguration of the specimen transferring unit 4. In addition, in thecase of this system, once an extracted micro-specimen 40 has been fixedto a TEM-specimen holder 19′, the TEM stage 114 can be taken out fromthe specimen chamber 77 and mounted on a TEM apparatus as it is. Thus, alengthy manual work requiring a skill of a well trained person is notneeded till an observation using a TEM. As a result, the length of timeit takes to fabricate a micro-specimen 40 can be reduced considerably,resulting in an effect of substantial reduction of a strain on thenerves caused by the work to fabricate the micro-specimen 40. Inaddition, in case an observation using a TEM is difficult to carry outdue to, among other reasons, the fact that a portion of the wafer 2 tobe observed, that is, the wall portion, is excessively thick, the methodoffers a convenience that the TEM stage 114 is simply brought again asit is into the specimen chamber 77 of the apparatus for fabricating themicro-specimen 40, allowing a re-fabrication by irradiation of an FIB tobe performed right away.

4-3 [Embodiment of the TEM-Specimen Holder]

As a conventional TEM-specimen holder, among other types, a single-holetype shown in FIG. 7/(a) and a mesh-type shown in FIG. 7/(b) are known.A single-hole-type holder 78 has a hole 79 with a diameter of 1 mmφprovided at the center of a thin metallic circular disc. When asingle-hole-type holder 78 is used, it is necessary to position amicro-specimen 79 on the inner surface wall of the hole 79 with a highdegree of accuracy and install the specimen 79 thereon. Since amicro-specimen 40 obtained by adopting the method for fabrication of aspecimen provided by the present invention has a small size in the range10 to 20 microns, the work to position the micro-specimen 40 is verydifficult to do. On the other hand, a mesh-type holder 109 has ametallic mesh 109′ stretched over an opening at the center of a thinmetallic circular disc. Thus, by using a metallic mesh 109′ with a gapbetween mesh nodes adjusted to the size of the micro-specimen 40, theposition at which the micro-specimen 40 is to be installed can beselected arbitrarily to a certain degree. With the mesh-type holder 109,however, the path of an electron beam passing through the micro-electron40 is shielded by a mesh structure member, making an observation using aTEM impossible in some cases.

As described above, an extracted micro-specimen 40 obtained by adoptingthe method for fabrication of a specimen provided by the presentinvention has a small size, strictly speaking, a height, in the range 10to 20 microns. Thus, if a dent with depth of at least 20 microns isprovided on the specimen fixing area of the holder, the extractedmicro-specimen 40 will be embedded in the dent, causing an electron beamfor observation to be shielded during an observation using a TEM. As aresult, it is impossible to perform an observation using a TEM on themicro-specimen 40 which was extracted from the specimen substrate 2 withmuch trouble. In order to solve this problem, in this embodiment, aspecimen holder shown in FIG. 26 is employed. The specimen holder isdesigned into such a structure that the direction of irradiation of anFIB during a fabrication using the FIB is perpendicular to the incidencedirection of an observation electron beam used during an observationutilizing a TEM so that both the FIB and the electron beam are notshielded. In addition, the flatness of a specimen fixing surface isimproved in particular in order to make the electron beam forobservation easy to irradiate.

In a holder 126 shown in FIG. 26/(a), an extracted micro-specimen 40 isheld on a sliver of silicon 127 cut out from a silicon wafer by using acleaving tool or a dicing saw. In this example, the holder 126 is cutout from a silicon wafer to have a size with a length of 2.5 mm, a widthof 50 microns and a height of 0.5 mm, that is, the thickness of thesilicon wafer. By using the ground surface of the silicon wafer as asurface for fixing the extracted micro-specimen 40, the amount ofunevenness of the fixing surface can be reduced. Thus, irradiation ofthe electron beam for observation is not obstructed during anobservation using a TEM. It should be noted that the dimensions andshape of the holder 126 are not limited to those shown in theembodiment. In a word, it is necessary to use the ground surface of thesilicon wafer as a surface for fixing an extracted micro-specimen 40 andto make the width of the holder 126 as small as possible.

A holder 128 shown in FIG. 26/(b) is an example of a modified version ofthe holder 126 shown in FIG. 26/(a). In the case of the holder 126, itis desirable to make the width of the holder 126 as small as possible soas to prevent irradiation of an electron beam for observation from beingobstructed due to a slight inclination of the holder 126 during anobservation using a TEM. If the width of the holder 126 is madeextremely small, however, the mechanical strength of the holder 126deteriorates, raising a problem such as a handling damage inflicted onthe holder 126. In order to solve this problem, in the case of theholder 128 shown in FIG. 26/(b), the holder 128 is designed into astructure that provides a sufficient mechanical strength and nohindrance to irradiation of an electron beam. To put it in detail, asliver of silicon 129 is cut out from a silicon wafer with a wide bottom129A and a narrow top 129B. That is, the cross section of the piece ofsilicon 129 has a convex shape which consists of two rectangles that arecontacted at the sides. An extracted micro-specimen 40 is mounted on thesurface of the narrow top 128B, that is, the ground surface of theoriginal silicon wafer. In the example shown in FIG. 26/(b), a pluralityof micro-specimens 40, to be more specific, 3 micro-specimens 40, aremounted on the holder 128.

A holder 130 shown in FIG. 26/(c) is created as a silicon plate 131having a semi-circular shape by applying a cleaving or wet-etchingtechnology to a silicon wafer. The holder 130 has a diameter of about 3mm and a thickness of about 50 microns. The surface for fixing anextracted micro-specimen 40 is the cleaved surface of the originalsilicon wafer which has enough smoothness. Since this holder 130 has asemi-circular shape, by using a ring-shape washer, the holder 130 can bemounted on a TEM stage 114 with ease.

A holder 132 shown in FIG. 26/(d) has a structure wherein the holder 126shown in FIG. 26/(a) is attached to a metallic board 133 having asemi-circular shape. The metallic board 133 having a semi-circular shapeis a thin plate having a thickness of 50 microns and a diameter of 3 mm.The holder 126 attached to the metallic board 133 is a sliver of silicon127 having a length of about 2 mm, a width of about 50 microns and aheight of about 0.5 mm. While electro-conductive adhesive is used forsticking the silicon holder 126 to the metallic board 133 in thisexample, another kind of adhesive is also usable. It should be notedthat the silicon holder 126 is stuck to the metallic board 133 in such away that the upper surface of the sliver of silicon 127 is placed at alevel higher than the upper surface of the metallic board 133 in orderto prevent an electron beam for TEM observation from being shielded bythe metallic board 133. In the case of the holder 126, the surface forfixing an extracted micro-specimen 40 is the ground surface of theoriginal silicon wafer which is adequately smooth. Since an extractedmicro-specimen 40 is not fixed to the upper surface of the metallicboard 133, on the other hand, the surface may be uneven to a certaindegree, providing no obstacle to an observation using a TEM at all.Thus, since the work to fabricate the metallic board 133 is hardly agreat strain on the nerves, the metallic board 133 can be fabricatedwith ease and at a low cost by adopting typically a punching method, awet-etching method or electric-discharge machining method. As describedabove, in the example shown in FIG. 26/(d), the holder 126 shown in FIG.26/(a) is attached to the metallic board 133. It should be noted,however, that the holder 128 shown in FIG. 26/(b) can be used in placeof the holder 126 shown in FIG. 26/(a) to give entirely the same effect.

4 embodiments implementing specimen holders having different shapes foruse in observations using a TEM have been explained. The basic conceptembraced by the 4 embodiments is to make the surface for fixing anextracted micro-specimen extremely smooth and the width of the surfaceas small as possible. It is needless to say that a variety of versionsbased on this concept can be implemented.

Fifth Embodiment

In order to separate an infinitesimal micro-specimen 40 from a specimensubstrate 2, a process to separate the bottom of the micro-specimen 40to be extracted from the substrate 2 is indispensable. The process toseparate the bottom of the micro-specimen 40 to be extracted from thespecimen substrate 2 is referred to as a bottom-dividing process. In theconventional bottom-dividing fabrication method using an FIB explainedearlier by referring to FIG. 4 and disclosed in prior-art reference 3,the FIB is irradiated in a direction slanting with respect to thesurface of the specimen substrate 2 in order carry out thebottom-dividing fabrication. Thus, a slope is generated on the bottom ofthe extracted specimen surface 2. The slope is determined by thefabrication aspect ratio and the incidence angle of the FIB irradiatedduring the bottom-dividing fabrication. In the conventional methoddescribed above, the bottom-dividing fabrication is performed, that is,a trench 34 for separation is created. Thus, a large slope of about 70degrees is resulted in on the specimen substrate. 2. If the distancebetween the objective lens 50 and the specimen substrate 2 required bythe focusability of the FIB is taken into consideration, in order tokeep the performance of the normally used FIB apparatus, the inclinationangle of the specimen substrate 2 should not exceed 60 degrees. Inaddition, inclination of the sample stage 3 for mounting a wafer 2having a large diameter of 300 mm by an angle of 70 degrees is verydifficult to implement from the mechanical point of view. Even if alarge inclination angle of 70 degrees is possible, when the extractedmicro-specimen 40 is mounted on the horizontal holding surface of theTEM-specimen holder, the surface of the micro-specimen 40 will form anangle of 20 degrees with the horizontal holding surface of theTEM-specimen holder because the bottom of the extracted micro-specimen40 has an inclination of 20 degrees. As a result, it is difficult tocreate a trench and a wall on the micro-specimen 40 perpendicularly tothe surface of the micro-specimen 40. In order to create a trench and awall on the micro-specimen 40 perpendicularly to the surface of themicro-specimen 40, it is necessary to reduce the inclination of thebottom of the micro-specimen 40 and to make the bottom approximatelyparallel to the top surface of micro-specimen 40. To make the bottomapproximately parallel to the top surface of micro-specimen 40, however,the inclination angle of the specimen substrate 2 during thebottom-dividing fabrication needs to be further increased, giving riseto more difficulties due to existing restrictions imposed on theconfiguration of the apparatus described above. For this reason, inorder to mount an extracted micro-specimen 40, at which the presentinvention is aimed, on another member (that is, a TEM-specimen holder)and to introduce them into an apparatus for observation or analysis, abottom-dividing method capable of creating a horizontal bottom or avertical side surface needs to be studied. It should be noted that, inthe method described in prior-art reference 3, the extractedmicro-specimen is observed with the micro-specimen firmly held on thetip of a probe as it is without the need to mount the micro-specimen ona TEM-specimen holder. Thus, the observation is not affected by theshape of the bottom of the micro-specimen whatsoever.

In order to solve the problems described above, there has been studiedan embodiment for implementing a method capable of extracting aninfinitesimal micro-specimen 40 by bottom-dividing fabrication withoutthe need to incline the sample stage 3 at an extremely large angle.

The procedure of the method for fabrication of a specimen provided bythe present invention is explained below in concrete terms. In theexplanation, the method for fabrication of a specimen is exemplified bya technique of fabricating a specimen for an observation using a TEM,starting with a process to mark an area to undergo an observation usinga TEM and ending with a final thinning fabrication which all use an FIB.In order to clarify the procedure, the procedure is divided into someprocesses which are explained by referring to FIG. 27.

5-1 [Marking Process]

In the method for fabrication of a specimen, it is assumed that aninfinitesimal micro-specimen including an area to undergo an observationusing a TEM is separated and extracted from a specimen substrate. Forthis reason, it is feared that the position of the area to undergo anobservation using a TEM can no longer be identified during a process ofthinning the area to undergo an observation using a TEM on themicro-specimen separated and extracted from the specimen substrate (or awall forming process). In order to solve this problem, it is necessaryto put marks for identifying an area to undergo an observation using aTEM. With the specimen substrate still in a wafer or chip state, aposition on the specimen substrate can be verified by computation of aposition from CAD data or by means of an optical-microscope image or ascanning ion microscope (SIM). First of all, marks are put on an area tobe observed (or a wall formation area). In this marking process, marksare put typically at both ends of the wall formation area by FIB orlaser fabrication. In this embodiment, 2 cross marks 134 and 134′ areput to sandwich the area to be observed, being separated away from eachother by a distance of 10 microns. The posture of the sample stage 3 isadjusted in advance so that a straight line connecting the marks 134 and134′ to each other is oriented in parallel to the inclination axis ofthe sample stage 3. In order to protect a wall 146 during the markingprocess, a deposition film not shown in the figure may be created asshown in FIG. 27/a.

5-2 [Rectangular-Hole Fabrication Process]

On the extension lines on both ends of the straight line connecting themarks 134 and 134′ to-each other, 2 rectangular holes 136 and 136′ arebored on the outer sides of the marks 134 and 134′ by irradiation of anFIB 135. Each of the rectangular holes 136 and 136′ has the followingtypical opening dimensions: an area of 10 microns×7 microns and a depthof about 15 microns. The rectangular holes 136 and 136′ are separatedfrom each other by a distance of 30 microns. It should be noted that, inorder to carry out the fabrication of the rectangular holes 136 and 136′in a short period of time, a large FIB with a beam diameter of about0.15 microns and a beam current of about 10 nA is used. As a result, thefabrication of the rectangular holes 136 and 136′ can be completed in 7minutes. Refer to FIG. 27/a.

5-3 [Vertical-Trench Fabrication Process]

Then, a thin long vertical trench 137 with a width of about 2 microns, alength of about 28 microns and a depth of about 15 microns is created byFIB scanning. The trench 137 is parallel to the straight line connectingthe marks 134 and 134′ and separated away from the line by a distance ofabout 2 microns. One end of the trench 137 reaches the rectangular hole136′ while the other end barely reaches the other rectangular hole 136.The direction of the FIB scanning is determined in such a way thatsputter particles generated by irradiation of an FIB 135 do not fill upthe vertical trench 137 and the rectangular holes 136 and 136′ whichhave been created at great pains. A residual area 138 left between therectangular hole 136 and the vertical trench 137 with a width of about 2microns serves as a support area for temporarily supporting amicro-specimen 40 including an area to be observed when themicro-specimen 40 is separated from the specimen substrate 2. Refer toFIG. 27/b.

5-4 [Diagonal-Trench Fabrication Process]

The surface of the specimen substrate 2 which has been held horizontallylevel in processes 5-1 and 5-2 is slightly inclined typically by 20degrees in this embodiment. Then, an inclined trench 139 is created inparallel to the straight line connecting the marks 134 and 134′ on theside opposite to the vertical trench 137 by FIB scanning. The trench 139is separated away from the line connecting the marks 134 and 134′ by adistance of about 2 microns. Since the straight line connecting themarks 134 and 134′ is set in parallel to the inclination axis of thesample stage 3 which is not shown in the figure, the surface of thespecimen substrate 2 is inclined so that the inclined trench 139 is putat a level higher than the vertical trench 137. Created to connect therectangular holes 136 and 136′, the inclined trench 139 has a width ofabout 2 microns, a length of about 30 microns and a depth of about 18microns. Also in this case, care must be exercised so that sputterparticles generated by irradiation of an FIB 135 do not fill up thevertical trench 137, the inclined trench 139, the rectangular hole 136and the rectangular hole 136′ which have been created at great pains.The bottom of the inclined trench 139 is merged with the bottom of thevertical trench 137. As a result, a micro-sample 140 with aright-angled-triangular cross section having a wedge like shape with abottom vertex of 20 degrees is separated from the specimen substrate 2with the residual area 138 left between the rectangular hole 136 and thevertical trench 137 serving as a support area. The separatedmicro-specimen 140 is supported by the support area 138. Refer to FIG.27/c.

5-5 [Deposition Process for Probe Fixation]

Then, after the surface of the specimen surface 2 is restored to thehorizontal level, the tip of the probe 141 employed in the specimentransferring unit 4 is brought into contact with the end of themicro-specimen 140 on the side opposite to the support area 138. Thecontact state can be sensed by detecting a change in electricalconduction and a change in capacity between the micro-specimen 140 andthe probe 141. In order to prevent a damage from being inflicted uponthe probe 141 and the micro-specimen 140 due to careless pressing of theformer against the latter, there is provided a function for halting thedriving in the downward direction, that is, the pressing down, of theprobe 141 as soon as the tip of the probe 141 comes in contact with themicro-specimen 140. Then, the tip of the probe 141 is firmly joined tothe micro-specimen 140 by a deposition film 142 created on an area towhich the FIB 135 is irradiated, strictly speaking, over which the FIB135 sweeps in a scanning operation, while gas for deposition is beingsupplied to an area with an angle of about 2 microns including the tipof the probe 141. That is, the tip of the probe 141 is firmly joined tothe micro-specimen 140 through the deposition film 142. Refer to FIG.27/d and e.

5-6 [Micro-Specimen Extraction Process]

In order to extract the micro-specimen 140 from the specimen substrate2, the FIB 135 is irradiated to the support area 138 holding themicro-specimen 140. The irradiation of the FIB eliminates the supportarea 138, releasing the micro-specimen 140 from the temporary heldstate. The support area 138 has an area of 2 square microns and a depthof about 15 microns which require an FIB irradiation (or scanning) ofabout 2 to 3 minutes to remove the support area 138. After the supportarea 138 has been removed, the micro element 140 is in a state of beingcompletely separated and extracted from the specimen substrate 2. Referto FIG. 27/e and f.

5-7 [Micro-Specimen Transfer (Sample Stage Shifting) Process]

Then, the micro-specimen 140 separated and extracted from the specimensubstrate 2 is moved to a TEM-specimen holder 143 with themicro-specimen 140 firmly attached to the tip of the probe 141 as it is.In actuality, it is the sample stage 3 that is shifted so that theTEM-specimen holder 143 mounted on the sample stage 3 is moved into thescanning range of the FIB 135. At that time, in order to avoid anunexpected accident, the micro-specimen 140 is saved at a position by amovement in the upward direction along with the probe 141 as shown by anarrow. As described earlier, there are a variety of methods for mountingthe TEM-specimen holder 143 on the sample stage 3. In this example, itis assumed that the TEM-specimen holder 143 has been mounted on a TEMstage of the side-entry type. Refer to FIG. 27/f and g.

5-8 [Micro-Specimen Fixation Process]

As the TEM-specimen holder 143 enters the scanning range of the FIB 135due to a shift of the sample stage 3, the shift of the sample stage 3 isdiscontinued on the spot. Then, the probe 141 is moved downward to bringthe micro-specimen 140 into contact with the TEM-specimen holder 143.Refer to FIG. 27/g.

As the tip of the micro-specimen 140 comes in contact with the uppersurface of the TEM-specimen holder 143, a deposition film 145 is createdat the contact location by irradiating the FIB 135 to the contactmembers while supplying gas for deposition to the contact members. Inthis way, the tip of the micro-specimen 140 is firmly joined to theupper surface of the TEM-specimen holder 143. In this embodiment, thedeposition film 145 is created on a longitudinal-direction end surfaceof the micro-specimen 140. At that time, the area of a portion to whichthe FIB 135 is irradiated is about 3 square microns. Part of the createddeposition film 145 is stuck on the TEM-specimen holder 143 whereas therest is attached to a side surface of the micro-specimen 140 so that thefilm 145 firmly joins the holder 143 to the specimen 140. It should benoted that, as an alternative technique, in order to fix themicro-specimen 140 to the TEM-specimen holder 143 with an even higherdegree of reliability, a thin long trench 144 with a width of about 2microns, a length of about 32 microns and a depth of about 3 microns iscreated in advance on the specimen fixing surface of the TEM-specimenholder 143 by fabrication using an FIB. Then, after the bottom of themicro-specimen 140 is inserted into the thin long trench 144, adeposition film 145 is created on a longitudinal-direction end surfaceof the micro-specimen 140. As a matter of fact, FIG. 17/(g) and (h) arediagrams showing this alternative technique.

It is desirable to place the area on the micro-specimen 140 to beobserved on the rotational-center axis of the TEM stage of theside-entry type. Since the micro-specimen 140 to be firmly joined to theTEM-specimen holder 143 has an infinitesimal size in the range severalmicrons to several tens of microns, however, in actuality, it will besufficient to bring the specimen fixing surface of the TEM-specimenholder 143 to the rotational-center axis of the TEM stage of theside-entry type. By doing so, the area on the micro-specimen 140 to beobserved can be brought into the observation visual field of a TEM whenthe TEM stage is set in the TEM.

In addition, if at that time, the rotational-center axis of the TEMstage of the side-entry type is oriented in a direction parallel to theinclination axis of the sample stage 3, it will be no longer necessaryto rotate the direction of the extracted micro-specimen 140. Thus, it isnot necessary to install a complex rotating mechanism in the specimentransferring unit 4. In addition, there is exhibited an effect that, byemploying a TEM stage of the side-entry type, the micro-specimen 140 canbe introduced into the TEM right after its fabrication. Another effectis that, when an additional fabrication is required, the micro-specimen140 can be returned to the FIB apparatus to undergo the additionalfabrication.

5-9 [Probe Separating Process]

After the operation to supply deposition gas has been halted, an FIB 135is irradiated to the deposition film 145 that firmly binds the tip ofthe probe 141 and the micro-specimen 140 together to eliminate thedeposition film 145 by a sputtering process. As the deposition film 145is eliminated, the probe 141 is detached from the micro-specimen 140. Inthis way, the micro-specimen 140 is firmly held by the TEM-specimenholder 143 and is put in a state completely independent of the probe141. Refer to FIG. 27/i.

5-10 [Thinning Process]

Finally, the desired area on the micro-specimen 140 to be observed issubjected to a thinning finishing process to produce a wall 146 with athickness not exceeding a value of about 100 nm. This thinning processis the last one of the sequence of processes to fabricate a TEMspecimen. Since one of the longitudinal-direction side surfaces of themicro-specimen 140 is a vertical surface, an area subjected to radiationof an FIB for this thinning process is determined by taking thisvertical surface as a reference. Thus, it is possible to create a wall156 that is all but perpendicular to the surface of the originalspecimen substrate 2. In addition, in order to fabricate the surface ofthe wall 146 into a flatter level, an FIB deposition film can be createdon the surface of the micro-specimen 140 including the wall formationarea prior to the irradiation of the FIB. As a result of the thinningprocess described above, it is possible to form a wall with a horizontalwidth of about 15 microns and a depth of about 10 microns, allowing aspecimen for use in an observation utilizing a TEM to be produced. Referto. FIG. 27/j.

All the processes described above, from the marking process to thethinning process, take about 1 hour and 30 minutes to complete, showinga reduction to a fraction of the length of time it takes to finish theprocesses according to the conventional methods for fabrication of a TEMspecimen.

5-11 [TEM-Observation Process]

After the thinning process described above has been completed, the TEMstage of the side-entry type is pulled out from the specimen chamber 77of the FIB apparatus for fabricating a TEM specimen and brought into aTEM-specimen chamber. At that time, the TEM stage is rotated so that thepath of an electron beam for observation crosses the wall surfaceperpendicularly before being brought into the TEM-specimen chamber.Generally known, the technology of the observation using a TEM carriedout thereafter is not explained.

As described above, the procedure for fabricating a specimen asimplemented by the embodiment applies to a specimen for observationusing a TEM. It should be noted, however, that applications of theprocedure are not limited to such a specimen. For example, the methodcan also used as a variety of other observation, analysis andmeasurement methods.

It is worth noting that the method for fabrication of a specimenprovided by this embodiment is much different from the specimenfabrication method disclosed in prior-art reference 3 in that:

(1) The method for radiation of a beam during extraction and separationof a specimen is completely different. In the case of the presentembodiment, in order to thin an extracted micro-specimen as much aspossible and to simplify the separation (the bottom-dividing process) ofthe bottom of the micro-specimen from the specimen substrate, aninclination process of a specimen longitudinal-direction side surface iscarried out. By the longitudinal direction, a direction parallel to theTEM observation surface is implied.

(2) In the case of this embodiment, an extracted micro-specimen isfirmly held by a TEM-specimen holder, a member completely different fromthe probe of the specimen transferring unit.

As described above, according to the method for fabrication of aspecimen provided by this embodiment, after marks are put on an area tobe observed or analyzed on a specimen substrate such as a wafer or adevice chip, a specimen for observations using a TEM, analyses,measurements or other kinds of observation can be fabricated from thespecimen substrate immediately without manual work and without takingthe specimen substrate from the vacuum specimen chamber of a specimenfabrication apparatus to a place outside the chamber. In addition, byusing the specimen fabrication apparatus provided by the presentembodiment, all the specimen-fabrication processes, from the markingprocess to the thinning process, can be carried out in a uniform mannerby using only the sample-fabrication apparatus. As a result, it ispossible to carry out a variety of operations, from extraction of amicro-specimen from mainly a semiconductor wafer and a semiconductorchip in addition to other materials and components to mounting of themicro-specimen on a TEM-specimen holder, without lengthy manual workrequiring much training and skills such as grinding and the mounting ofthe micro-specimen on the TEM-specimen holder and with reducedpossibility of risks such as dropping of a specimen during a transfer ofthe specimen from equipment to equipment. In particular, the length oftime it takes to fabricate a TEM specimen can be reduced substantially.

Sixth Embodiment

When a probe is brought into contact with the surface of a specimensubstrate by a specimen transferring unit in order to extract amicro-specimen from the specimen substrate, it is necessary to exercisecare so as to prevent a damage or an injury from being inflicted uponthe specimen substrate. This embodiment implements a specimentransferring method and a specimen transferring unit taking preventionof infliction of an injury on a specimen substrate into consideration.

FIG. 28 is a diagram showing the configuration of a specimentransferring unit (or a manipulator) as implemented by this embodimentin a simple and plain manner. As shown in the figure, the specimentransferring unit 4 comprises a probe 11 for holding an extractedmicro-specimen, a coarse-movement actuator 147 for moving the probe 11in the 3 directions of the X, Y and Z axes at a low movement resolutionand a fine-movement actuator 148 for moving the probe 11 in the Z-axialdirection at a high movement resolution. The coarse-movement actuator147 is installed at a location sufficiently separated away from a samplestage which is not shown in the figure. In order to allow the probe 11attached to the fine-movement actuator 158 to make accesses to a widerange of locations on the sample stage, the fine-movement actuator 148is connected to the coarse-movement actuator 147 through a longextension rod 149.

The coarse-movement actuator 147 comprises an X-axial-directionsub-actuator 147X, a Y-axial-direction sub-actuator 147Y and aZ-axial-direction sub-sub-actuator 147Z. The movement stroke is about 3mm and the movement resolution is about 0.5 microns in each of the 3axial directions. The fine-movement actuator 148 is implemented by abimorph-type piezoelectric device with a movement stroke of about 200microns and a movement resolution of about 0.05 microns.

As described above, the fine-movement actuator 148 is connected to thecoarse-movement actuator 147 through the long extension rod 149 for areason described as follows. In a space between an ion-beam irradiatingoptical system and a final-stage lens electrode employed in the specimenfabrication apparatus provided by the present invention and in thesurrounding spaces, a variety of components coexist. In order to avoidcontention for space with the variety of components, it is desirable toinstall the coarse-movement actuator 147, the main body of the specimentransferring unit 4 provided by the present invention, at a location asseparated away as possible from the sample stage. In this embodiment, byusing the extension rod 149, the coarse-movement actuator 147 can beinstalled at a location separated away from the sample stage.

A procedure for bringing the tip of the probe 11 into contact with thesurface of a specimen substrate 2 is explained by referring to FIG. 29.In FIG. 29, a point 151, an intersection of a dotted line 150 and thesurface of the specimen substrate 2, is the target contact position ofthe probe 11.

FIG. 30 is a flowchart used for explaining the procedure comprisingprocedural steps shown in FIG. 29/(a)-(f) for bringing the tip of theprobe 11 into contact with the surface of the specimen substrate 2 shownin FIG. 29. It should be noted that, in the flowchart shown in FIG. 30,the symbol ‘Y’ appended to an arrow indicates the occurrence of anevent. For example, if the event is contact check, the symbol ‘Y’indicates that the contact check has been carried out. On the otherhand, the symbol ‘N’ appended to an arrow indicates the non-occurrenceof an event. For example, if the event is contact check, the symbol ‘N’indicates that the contact check has not been carried out. Unlessotherwise stated differently, the word ‘contact’ used in the flowchartshown in FIG. 30 means contact between the tip of the probe 11 and thesurface of the specimen substrate 2. It should be noted that, inactuality, the state of contact between the tip of the probe 11 and thesurface of the specimen substrate 2 is always monitored, that is, thework to check the contact is done all the time. Thus, when there iscontact, an operation indicated by an arrow appended by the symbol ‘Y’is carried out. In the following description, the phrase ‘contact check’appears a number of times. Thus, in order to avoid redundantexplanation, the detailed description of the contact-check event isomitted except for special cases.

First of all, after confirming that the tip of the probe 11 is not incontact with the surface of the specimen substrate 2, theX-axial-direction sub-actuator 147X and the Y-axial-directionsub-actuator 147Y are driven to move the tip of the probe 11 to aposition right above the target contact position 151 as shown in FIG.29/(a). Then, with the tip of the probe 11 located at a positionseparated away from the surface of the specimen substrate 2 by adistance of at least equal to the total stroke of the fine-movementactuator 148, the fine-movement actuator 148 is driven to bring the tipof the probe 11 closer to the surface of the substrate 2 from the originof the fine-movement actuator 148 by a distance Z0 as shown in FIG.29/(b). Typically, the distance Z0 is about 50% of the total stroke ofthe fine-movement actuator 148. Thus, in this embodiment, assuming thatthe total stroke is 200 microns, Z0 is about 100 microns. Then, theZ-axial-direction coarse-movement sub-actuator 147Z is driven to makethe fine-movement actuator 148 approach the surface of the specimensubstrate 2 till the tip of the probe 11 comes in contact with thesurface of the specimen substrate 2 as shown in FIG. 29/(c). The contactbetween the tip of the probe 11 and the surface of the specimensubstrate 2 can be confirmed typically by monitoring changes inelectrical resistance between the tip of the probe 11 and the surface ofthe specimen substrate 2. As an alternative, the contact between theprobe 11 and the surface of the specimen substrate 2 can be confirmed byapplying a voltage to the probe 11 in advance and then monitoringchanges in voltage contrast on a secondary-electron image of the surfaceof the specimen surface 2. As the contact between the probe 11 and thesurface of the specimen substrate 2 is confirmed in this way, themovement of the Z-axial-direction coarse-movement actuator 147Z ishalted at once and the fine-movement actuator 148 is driven again to letthe tip of the probe 11 escape to the origin (a 0-micron position), thatis, to swing upward to the 0-micron position. By letting thefine-movement actuator 148 escape from the surface of the specimensubstrate 2, the tip of the probe 11 is restored to a positionsufficiently separated from the surface of the specimen substrate 2,that is, a position separated from the surface of the specimen substrate2 by an escape distance of about 100 microns, so that, no injury isinflicted upon both the tip of the probe 11 and the surface of thespecimen substrate 2 even if the tip of the probe 11 has been broughtinto excessive approach with the surface of the specimen substrate 2 toa certain degree due to causes such as a drift or a lag of stopping ofthe Z-axial-direction coarse-movement actuator 147Z. Thus, the stroke ofthe fine-movement actuator 148 has to be sufficiently greater than adistance of the excessive approach due to causes such as a drift or alag of stopping of the Z-axial-direction coarse-movement sub-actuator147Z. In the case of the specimen transferring unit (the probe drivingmechanism) 4 provided by the present invention, for example, thedistance of the excessive approach of the Z-axial-directioncoarse-movement sub-actuator 147Z is smaller than 1 micron and thestroke of the fine-movement actuator 148 is 200 microns as describedabove. Thus, since the escape distance of the fine-coarse actuator 148is 100 microns which is 50% of the stroke, the escape distance cantherefore sufficiently prevent an injury from being inflicted upon boththe tip of the probe 11 and the surface of the specimen substrate 2. Forthe sake of more safety, the operation of the Z-axial-directioncoarse-movement sub-actuator 147Z is looked and the Z--axial-directioncoarse-movement sub-actuator 147Z can not thus be driven again as longas nothing is done to deliberately release the Z-axial-directioncoarse-movement sub-actuator 147Z from the locked state. Refer to FIG.29/(d). In this state, the X-axial-direction sub-actuator 147X and theY-axial-direction sub-actuator 147Y are driven to finally adjust theposition of the tip of the probe 11 to a location right above the targetcontact position 151 as shown in FIG. 29/(e). Finally, only thefine-movement actuator 148 is driven to bring the tip of the probe 11into contact with the surface of the specimen substrate 2 softly asshown in FIG. 29/(f). Since the final contact can be established by onlythe fine-movement actuator 148 in this way, it is possible to prevent aninjury from being inflicted upon both the tip of the probe 11 and thesurface of the specimen substrate 2.

FIG. 30/(g) is a flowchart showing a method of adjustment which isadopted in case there is a positional shift after contact has beenestablished. However, FIG. 29 does not include a diagram showing thisadjustment procedure. As shown in the flowchart of FIG. 30/(g), if theactual contact position is shifted from the target contact position, thefine-movement actuator 148 is driven to escape in the upward directionso that the tip of the probe 11 is released from the contact state withthe surface of the specimen substrate 2. If the tip of the probe 11 istill in contact with the surface of the specimen substrate 2 even afterthe fine-movement actuator 148 has been restored to the origin, that is,the 0-micron position, the Z-axial-direction sub-actuator 147Z isreleased from the locked state and the probe 11 is driven into a coarsemovement in the Z-axial direction to let the tip thereof further escape.Then, the operation to move the tip of the probe 11 is resumed from anapproaching operation by a coarse movement in the Z-axial direction.Even if the escaping fine movement by the fine-movement actuator 148releases the tip of the probe 11 from the contact state with the surfaceof the specimen substrate 2, for caution's sake, the probe 11 is furtherdriven upward by the fine-movement actuator 148 to let the tip thereofescape farther by a distance Z1. The value of Z1 is determined by thedistances of movements by the tip of the probe 11 on the XY plane andthe amount of the unevenness of the surface of the specimen substrate 2.Then, the X-axial-direction sub-actuator 147X and the Y-axial-directionsub-actuator 147Y are driven to take the tip of the probe 11 to alocation right above the target contact position 151 as shown in FIG.29/(e). Finally, only the fine-movement actuator 148 is driven to letthe tip of the probe 11 approach the surface of the specimen substrate 2and to bring the former into contact with the latter.

If a distance causing excessive approach caused by a creep or a lag ofcoarse-movement stopping described above can be estimated in advance,the escaping fine movement shown in FIG. 29/(d) is not necessarily madeover a long distance of 100 microns from the Z0 position (or the100-micron position) to the origin (or the 0-micron position). Forexample, if a distance causing excessive approach is estimated to be 5microns or shorter, the distance of the escaping fine movement can beset at about 10 microns, or a distance from the 100-micron position tothe 90-micron position. As an alternative, the fine-movement actuator148 can be driven to once restore the tip of the probe 11 to the origin(the 0-micron position). Then, the probe 11 is driven to approach thesurface of the specimen substrate 2 till the 90-micron position at arelatively high speed. Thereafter, the driving of the probe 11 iscontinued at a sufficiently low speed till the vicinity of the100-micron position is reached. In this way, the tip of the probe 11 isbrought into contact with the surface of the specimen substrate 2 byadopting the so-called variable-speed approaching technique. In thiscase, since the approaching speed of the probe 11 prior to a contactstate is low, the probability of infliction of a damage on the specimensubstrate 2 decreases and the length of the total time to drive thefine-movement actuator 148 can also be reduced as well.

If driving the probe 11 at a high movement resolution by thefine-movement actuator 148 causes a small displacement in the XY plane,procedural step (e) for driving the X-axial-direction sub-actuator 147Xand the Y-axial-direction sub-actuator 147Y to finally adjust theposition of the tip of the probe 11 to a location right above the targetcontact position 151 after procedural step (d) for driving the probe 11at a high movement resolution to escape from the surface of the specimensubstrate 2 is not meaningful any more. Thus, in this case, afterprocedural step (b) for driving the probe 11 at a high movementresolution to approach the Z0 position, the tip of the probe 11 isdriven in the X and Y axial directions at a low movement resolution to aposition right above the target contact position 151. Then, proceduralsteps (c) and (d) are executed to be followed by procedural steps (f)and (g), skipping procedural step (e) as described above to give ahigher efficiency.

The method of bringing the tip of the probe 11 into contact with thesurface of the specimen substrate 2 has been described above. It shouldbe noted that the method can also be adopted to bring a micro-specimen40 into contact with the TEM-specimen holder 19 after the micro-specimen40 has been extracted from the specimen substrate 2. The description ofthe method of bringing the tip of the probe 11 into contact with thesurface of the specimen-substrate 2 holds true of the method to bring amicro-specimen 40 into contact with the TEM-specimen holder 19 if themicro-specimen 40 fixed on the probe 11 is substituted for the probe 11in the description and the surface of the TEM-specimen holder 19 issubstituted for the surface of the specimen substrate 2 in thedescription. Also in this case, it is needless to say that injuries canbe effectively prevented from being inflicted upon the micro-specimen 40and the TEM-specimen holder 19.

By adopting the method to bring a member into contact with anothermember described above, injuries can be effectively prevented from beinginflicted upon the probe, the specimen substrate and the TEM-specimenholder.

A variety of embodiments of the present invention have been describedabove. It should be noted, however, that the scope of the presentinvention is not limited to the embodiments. In the description, theembodiments are mainly exemplified by fabrication of specimens forobservations using a TEM. It is obvious, however, that the presentinvention can also be applied to fabrication. of specimens forobservations using other observation apparatuses such as an SEM andfabrication of specimens subjected to analyses and measurements.

As described above, according to the present invention, it is possibleto fabricate specimens for an observation apparatus such as a TEM orother types of apparatus such as an analysis/measurement apparatusdirectly from a specimen substrate such as an integrated-circuit chip ora semiconductor wafer without requiring manual work. In addition, sincea micro-specimen extracted from the substrate can be held in acartridge, the micro-specimen can be controlled and maintained withease. Moreover, the number of undesirable effects such as mechanicalvibration generated by an external source during an observation or ananalysis of the micro-specimen can be reduced.

POTENTIAL INDUSTRIAL APPLICATIONS

The method and apparatus for fabrication of specimens provided by thepresent invention can be utilized in fabrication of infinitesimalspecimens subjected to observations, analyses and measurements of asmall area on a substrate such as a semiconductor wafer or asemiconductor device chip. In particular, the method and apparatus areeffective for fabrication of specimens subjected to observation using aTEM. The method and apparatus contribute to facilitation ofclarification of causes of failures occurring during a process ofmanufacturing VLSI semiconductor devices.

1. A specimen fabrication apparatus comprising: an ion source, anoptical system for irradiating a projection ion beam to a sample,wherein the optical system includes a patterning mask to form a ion beamemitted from the ion source into the projection ion beam, a sample stageto mount the sample, a vacuum specimen chamber to contain the samplestage, a probe for separating a micro-specimen from the sample byirradiation of the projection ion beam, a specimen holder to fix themicro-specimen, wherein the projection ion beam is irradiated to themicro-specimen fixed to the specimen holder and extracted by the probein the specimen chamber, so that a finish fabrication to themicro-specimen is enabled.
 2. A specimen fabrication apparatus accordingto claim 1, wherein the sample is semiconductor wafer, semiconductorchip or device chip.
 3. A specimen fabrication apparatus according toclaim 1, comprising: an electron-beam irradiating optical system forirradiating an electron beam to the sample.
 4. A specimen fabricationapparatus comprising: an ion source; an optical system for irradiatingan ion bean emitted from the ion source via a patterning mask, tofabricate a micro-specimen from a sample; a probe for separating themicro-specimen from the sample, a specimen holder to mount themicro-specimen.
 5. A specimen fabrication apparatus comprising: an ionsource; an optical system for irradiating an ion beam emitted from theion source via a patterning mask, to fabricate a micro-specimen from asample; a probe for separating the micro-specimen from the sample, aspecimen holder to mount the micro-specimen, and an electron-beamirradiating optical system for irradiating an electron beam to thesample.
 6. A specimen fabrication apparatus comprising: an irradiatingoptical system to irradiate a sample with a projection ion beam, asample stage to mount the sample, a vacuum specimen chamber to containthe sample stage, a specimen holder in the vacuum specimen chamber tomount a micro-specimen which is extracted from the sample by theirradiation of the projection ion beam, and a transferring means tomount the micro-specimen to the specimen holder.
 7. A specimenfabrication apparatus according to claim 6, wherein the irradiatingsystem includes a patterning mask for the ion beam to pass through.
 8. Aspecimen fabrication apparatus according to claim 6, wherein thetransferring means includes a probe.
 9. A specimen fabrication apparatusaccording to claim 6, wherein the sample is semiconductor wafer,semiconductor chip or device chip.
 10. A specimen fabrication apparatusaccording to claim 6, comprising: an electron-beam irradiating opticalsystem for irradiating an electron beam to the sample.
 11. A specimenfabrication apparatus according to claim 6, wherein, with theirradiation of the ion beam to the micro-specimen fixed on the specimenholder, a specimen for transmission electron microscopy observation isfabricated.
 12. A specimen fabrication apparatus according to claim 6,wherein the specimen holder comprises a plurality of specimen holders.13. A specimen fabrication apparatus according to claim 6, wherein thespecimen holder is capable of mounting a plurality of themicro-specimens.